Microprocessor-based cordless telephone system

• US 4,467,140 A
• Filed: 05/01/1981
• Issued: 08/21/1984
• Est. Priority Date: 05/01/1981
• Status: Expired due to Fees

• Current Assignee: Southwestern Bell Telecommunications Incorporated
• Original Assignee: Masco Corporation Of Indiana (Masco Corporation)
• Inventors: Williamson, Warren L., Fathauer, George H.
• Primary Examiner(s): Rubinson, Gene Z.
• Assistant Examiner(s): Brady, W. J.
• Application Number:
  US06/259,787
• Time in Patent Office: 1,208 Days
• Field of Search: 179/2 E, 179/2 EA, 179/2 EB, 179/2 EC, 179/18 DA, 179/90 D, 179/90 B, 179/90 BD, 179/81 R, 455/68-70, 455/86, 455/87, 455/76, 455/89
• US Class Current: 455/462
• CPC Class Codes: H04M 1/72505 Radio link set-up procedures

Abstract

A cordless telephone system is provided which includes a base unit operatively coupled to a user'"'"'s telephone lines and a relatively compact portable cordless handset. Both the base unit and the cordless handset include a radio transmitter and a receiver which form a full duplex two-way FM radio link wherein the transmitter of the base unit and the receiver of the cordless handset operate on a first non-CB frequency and the transmitter of the cordless handset and the receiver of the base unit operate on a second different and distinct non-CB frequency. Both the cordless handset and the base unit include signal-injecting circuitry whereby a portion of the transmitter signal is injected into the input of the receiver to provide the local oscillator function for that receiver without undesirable cross-talk between the transmitted and received signals. The cordless handset also includes a keyboard for entering dialing information, security code identification switches for entering a user'"'"'s identification code, a logic network responsive to the entered dialing information and security code information for generating data words indicative thereof, and an FSK-encoder including circuitry for generating a subcarrier frequency tone and circuitry responsive to the subcarrier tone for generating FSK-encoded equivalents of the data words. The FSK-encoded data words and the subcarrier frequency tone are superimposed on an FM modulated carrier for transmission to the receiver of the base unit. The base unit includes a microprocessor-based control system for controlling substantially all operational functions including ringing signal generation, security identification, line seizure, dialing signal generation, memory storage and recall, muting during identification and dialing, selecting T/R or R/O operation, and the like.

Claims

1. A cordless two-way telephone system comprising:

a base unit operatively connected to a subscriber'"'"'s telephone lines;

a portable cordless handset for communicating with said base unit;

said base unit including a full duplex FM radio transceiver operating in a predetermined non-CB frequency band, said transceiver including a single antenna, a receiver and a transmitter, said receiver operating on a first channel frequency and said transmitter operating on a second channel frequency;

said base unit transceiver further including means for normally establishing a receive-only mode of operation;

means responsive to said receive-only mode of operation for supplying reduced power to said base unit transmitter for generating only that portion of transmitter signal required for providing the local oscillator function of said receiver;

means responsive to a transmit enable command for supplying full power to said base unit transmitter for establishing a transmit-receive mode of operation and for generating a relatively strong transmitter signal;

first coupling means for feeding said strong transmitter signal from the output of said transmitter to said single antenna for transmission to said cordless telephone handset and for feeding incoming signals transmitted by said cordless telephone handset from said single antenna to the input of said receiver, said first coupling means also passing at least that portion of said strong transmitter signal required for providing the local oscillator function of said receiver during the transmit-receive mode of operation;

first by-pass means normally by-passing said first coupling means to connect the transmitter output directly to the receiver input during the receive-only mode of operation for supplying that portion of the transmitter signal required for providing the local oscillator function of the receiver while eliminating substantially all undesirable coupling between transmitted and received signals;

means operatively coupled to said subscriber'"'"'s telephone lines for detecting in-coming ringing signals and generating a ring detection signal indicative thereof;

microprocessor means including means responsive to said ring detection signal for generating said transmit enable command and a local ringing signal;

means for coupling said local ringing signal to the base unit transmitter for transmission to said cordless telephone handset;

said cordless telephone handset including a full duplex FM radio transceiver operating in said predetermined non-CB frequency band, said transceiver including a single antenna, a receiver and a transmitter, said handset receiver operating on said second channel frequency for receiving signals broadcast by said base unit transmitter and said handset transmitter operating on said second channel frequency for transmitting signals to said base unit receiver;

said handset transceiver further including means for normally establishing the receive-only mode of operation;

means responsive to said receive-only mode of operation for supplying reduced power to said handset transmitter for generating only that portion of transmitter signal required to provide the local oscillator function of said handset receiver;

means responsive to said transmit enable command to establish said transmit-receive mode of operation for supplying full power to said handset transmitter for generating a relatively strong transmitter signal;

second coupling means for feeding said strong transmitter signal from the output of said handset transmitter to said single antenna for transmission to said base unit and for feeding incoming signals transmitted by said base unit from said single antenna to the input of the handset receiver, said first coupling means also passing at least that portion of said strong transmitter signal required for providing the local oscillator function of the handset receiver during the transmit-receive mode of operation;

second by-pass means normally by-passing said second coupling means for directly connecting the transmitter output to the receiver input during the receive-only mode of operation for supplying that portion of the transmitter signal required for providing the local oscillator function of the cordless handset receiver while eliminating substantially all undesirable coupling between transmitted and received signals;

means responsive to said transmit-receive mode of operation for disabling said second by-pass means;

said cordless telephone handset further including a microphone for generating audio signals from a user'"'"'s speech and means for frequency modulating said first frequency channel with said audio signals prior to transmission to said base unit;

a speaker for receiving signals from said handset receiver and audiblizing both a local ringing tone and speech information;

a first switching means for manually selecting a discrete security identification code;

a second switching means having a first switch position corresponding to an "on-the-hook" telephone condition and the second position corresponding to the cordless telephone handset being "off-the-hook" indicating that a user intends to use the cordless telephone handset;

a key pad for manually entering keyboard information including dialing codes and keyboard commands;

logic means responsive to said second switching means having been positioned to said off-the-hook position and to the security identification code selected by said first switching means for generating a discrete security identification code data word, said logic means further including means for generating a subcarrier frequency tone and means responsive to said keyboard information entered on said key pad for generating dialing code data words;

means responsive to said generated data words and to said subcarrier frequency tone for encoding frequency shift-keyed (FSK) equivalents of said data words;

said cordless handset including means for coupling said FSK-encoded data words, said subcarrier frequency tone, and said frequency modulated audio signals to said handset transmitter for transmission to said base unit;

said base unit also including means for detecting and decoding said FSK-encoded data words and generating digital data words indicative thereof;

means for storing a discrete security identification code for use by said microprocessor means in identifying an authorized user;

said microprocessor means including means for monitoring said digital data words, means for identifying a security identification code data word, and means for comparing an identified security identification code data word with said stored discrete security identification code to make a positive identification of an authorized cordless handset user and for generating a line seizure command in response to said identification;

means responsive to said line seizure command for seizing said subscriber'"'"'s telephone lines and maintaining control thereof so long as said subcarrier frequency tone is transmitted by said handset;

means responsive to said dialing code data words for generating conventional dialing signals indicative thereof; and

means for sending said conventional dialing signals and received audio signals over said seized telephone lines and for transmitting incoming signals from said seized telephone lines to the transmitter of said base unit for transmission to said cordless handset thereby enabling two-way communication between an authorized user of the cordless telephone handset and the party calling or being called on the telephone lines.

2. The cordless two-way telephone of claim 1 wherein said first and second coupling means of said base unit and said cordless handset, respectively, each includes a first crystal filter operatively coupled between the transmitter output and said single antenna for passing substantially only the transmitted one of said first and second channel frequency signals to its corresponding antenna and a second crystal filter operatively coupled between said single antenna and the receiver input for passing substantially only the received one of said first and second channel frequencies, the band path characteristics of said second crystal filter being such that at least said portion of the transmitter signal required for performing the local oscillator function of its corresponding receiver is passed by said second filter when said transceiver is in said transmit-receive mode of operation.

3. The cordless two-way telephone of claim 2 wherein said first and second by-pass means of said base unit and said cordless handset, respectively, each includes a direct electrical connection between the transmitter output and the receiver input in parallel with said first and second coupling means for directly injecting the normally weak transmitter signal into the receiver to provide the local oscillator function thereof during the transmit-receive mode of operation.

4. The cordless two-way telephone of claim 3 wherein said disabling including a switching element operatively coupled to said direct electrical connections and responsive to said transmit-receive mode of operation for switching to disable said connection.

5. The cordless two-way telephone of claim 1 further including a normally-open manually-positionable call switch whose output is operatively coupled to said microprocessor means, said call switch being normally closed to transmit a false ring detection signal to said microprocessor means for causing said microprocessor means to generate the transmit-receive command to power said transceiver means and generate said local ringing signal thereby enabling said call switch to be used for paging purposes.

6. The cordless two-way telephone of claim 1 wherein said first switching means includes a plurality of manually-operable switches for selecting a discrete security code identifying an authorized user.

7. The cordless two-way telephone of claim 1 wherein said key pad for manually entering keyboard information further includes key-operated means for indicating "on-the-hook" and "off-the-hook" conditions.

8. The cordless two-way telephone of claim 1 wherein said logic means further includes means responsive to particular key closures for generating memory address data words, said microprocessor means including memory means for storing at least one predetermined telephone number, and means responsive to said memory address data words for generating memory address commands in response thereto, and means responsive to said memory address commands for recalling said stored telephone number and automatically generating dialing signals in response thereto.

9. The cordless two-way telephone of claim 7 wherein said microprocessor means further includes additional memory means for automatically storing a dialing code data word representing the last telephone number called and for recalling same and automatically generating dialing signals corresponding thereto in response to a unique keyboard command entered on said key pad.

10. The cordless two-way telephone of claim 1 wherein said FSK-encoding means includes means for generating a second frequency tone different and distinct from said subcarrier frequency tone such that the logical zeroes and ones comprising said data words are transformed into corresponding FSK signals at said second frequency tone and at said subcarrier frequency tone, respectively.

11. The cordless two-way telephone of claim 1 wherein both of said transceiver means includes means for balancing out the locally-generated demodulation component.

12. The cordless two-way telephone of claim 1 wherein the handset transceiver means includes filtering means for filtering out the subcarrier frequency tone used to maintain acquisition of the seized telephone lines.

13. A cordless telephone comprising a portable cordless handset and a base unit;

said portable cordless handset including a microphone into which the user speaks for generating a microphone-produced signal, a speaker for outputting a ringing tone signal and audible speech, transceiver means for transmitting microphone-produced signals, subcarrier frequency tones, and data words to said base unit and for receiving a local ringing tone generated by said base unit and speech signals transmitted to said base unit via said telephone lines, said transceiver means supplying said local ringing tone signals and said speech signals to said speaker for audiblizing same, means for generating a discrete security code data word indicative of the user'"'"'s identification, switching means having a first position indicating a normally "off" condition such as normally exists when a telephone is hung up and an "on" condition which corresponds to that condition normally existing when a telephone is "off-the-hook", and means responsive to said switching means being in said "on" position for transmitting said security code data word to said base unit via said transceiver means;

said base unit operatively connected to a subscriber'"'"'s telephone lines, said base unit including transceiver means for transmitting a local ringing tone and speech signals to said cordless handset, said speech signals originally being transmitted over said telephone lines to said base unit, and for receiving microphone-produced signals, subcarrier frequency tones and data words from said cordless handset, means for storing a discrete security code identifying an authorized user, microprocessor means for receiving said security code data word from said handset and comparing same with said discrete stored security code and generating a line seizure command whenever an authorized user is identified, and means responsive to a line seizure command for seizing the telephone lines and maintaining acquisition thereof as long as the identified authorized user maintains said switching means in the "on" position; and

said transceiver means of both said cordless handset and said base unit each including a transmitter, an antenna, and a receiver, said transceiver means enabling full duplex two-way radio transmission between said base unit and said cordless handset, the transmitter of said cordless handset and receiver of said base unit operating on a first non-CB frequency and the transmitter of said base unit and receiver of said cordless handset operating on a second non-CB frequency, the transmitted frequencies of each of said transmitters acting as the local oscillator for the corresponding receiver of its respective transceiver means thereby enabling transmission and reception on a single antenna on each of said transceiver means while eliminating substantially all interference between transmitted and received signals.

14. The cordless telephone of claim 13 wherein said base unit includes means for detecting an in-coming ringing signal on said telephone lines and generating a ring detection signal in response thereto, said microprocessor means including means responsive to said ring detection signal for generating a local ringing signal and a transmit enable signal, said base unit further including a transmit enable switching means having a first normally non-conductive state for supplying a reduced amount of power to said transceiver means of said base unit, said reduced amount of power being sufficient to provide only that amount of transmitted signal necessary to provide adequate mixing operation for reception operation only, and a second conductive state for supplying full power to said transceiver means of said base unit for enabling full transmitter and receiver operations, said transmit enable switching means being responsive to said transmit enable signal from said microprocessor means for switching to said second state in response to the detection of a ringing signal and powering the base unit transceiver for transmitting the microprocessor means-produced local ringing signal to said cordless handset.

15. The cordless telephone of claim 13 wherein said microprocessor means includes means for generating a muting command during identification and dialing operations and means responsive to said muting command for aiding the transmitter modulation.

16. The cordless telephone of claim 13 wherein said cordless handset further includes a keyboard means and logic means for generating a keyboard-defined dialing code data word, said data word being transmitted by the transceiver means of said cordless handset to said base unit, said microprocessor means further including means responsive to said dialing code data word for generating dialing signals, said base unit further including means responsive to said dialing signals for enabling an authorized user to dial a selected telephone number via the subscriber'"'"'s telephone lines connected to said base unit.

17. A cordless telephone of claim 16 wherein said means responsive to said microprocessor-generated dialing signals includes touch tone encoder means responsive to said dialing signals for generating sequences of digital pulses for transmission to said telephone lines to perform the normal dialing functions.

18. The cordless telephone of claim 13 wherein said cordless handset further includes a keyboard for entering dialing codes and the like and a second switching means on said keyboard to enable the user of said cordless handset to more easily indicate an "off-the-hook" condition by activating said second switching means to indicate that he has answered the telephone.

19. The cordless telephone of claim 13 wherein said cordless handset further includes a keyboard and logic means for generating keyboard-defined command data words which are transmitted to said base unit via the transceiver means of said cordless handset, said microprocessor including memory means for storing at least one dialing code data word indicative of a predetermined telephone number, means responsive to the receipt of said keyboard-defined command data word for addressing said memory means and recalling said dialing code data word for generating telephone dialing signals corresponding thereto.

20. The cordless telephone of claim 13 wherein said means for generating a discrete security code data word in said cordless handset includes logic means for generating a subcarrier frequency pilot tone and means responsive to said pilot tone and said data word for generating an FSK-encoded equivalent of said data word for transmission to said base unit, said base unit further including means for decoding said FSK-encoded data word in said microprocessor including means responsive to said decoded data word for comparing same with said stored discrete security code and generating said line seizure command when an authorized user is identified.

21. The cordless telephone of claim 20 wherein said cordless handset further includes a keyboard, logic means for generating keyboard-defined dialing code data words, said FSK-encoding means being responsive to the said dialing code data words for encoding same for transmission to said base unit and the FSK decoder means of said base unit being responsive to said FSK-encoded dialing code data words for decoding same for transmission to said microprocessor, said microprocessor including means responsive to said decoded dialing code data words for generating dialing signals for normal transmission on said subscriber'"'"'s telephone lines.

22. The cordless telephone of claim 13 wherein said means for storing a discrete security code identifying an authorized user includes a plurality of manually-operable switches, means responsive to said plurality of manually-operable switches for generating said discrete security code, and memory means for storing said generated discrete security code for comparison purposes.

23. The cordless telephone of claim 20 wherein the continued generation of the subcarrier frequency pilot tone is controlled by the position of said switching means, said microprocessor being responsive to the continued receipt of said pilot tone after the initial seizure to maintain the telephone line acquisition after the initial line seizure until the on-off switch is turned off.

24. The cordless telephone of claim 13 wherein each of said transceiver means includes a first crystal filter for passing only the transmitted frequency signals from said transmitter output to the antenna, a second crystal filter for passing only the received frequency signals from said antenna to input of said receiver means, and means coupling said first and second crystal filters for supplying at least a portion of the transmitted signal to the receiver input for performing the local oscillator function.

25. The cordless telephone of claim 24 wherein each of said transceiver means also includes a direct signal injection path connected between the transmitter output and receiver input in parallel with said filters for injecting the relatively weak transmitter signal generated during the receive-only mode of operation into the receiver for providing the local oscillator function thereof.

26. The cordless telephone of claim 13 wherein at least one of said transceiver means includes means for balancing out the locally generated transmitter modulation from the demodulation of the received signal.

27. The cordless telephone of claim 13 further including memory means for storing at least one predetermined telephone number, said microprocessor means being responsive to a predetermined command for addressing said memory means and recalling said predetermined stored telephone number to generate a dialing signal indicative thereof, said base unit including automatic dialing means responsive to said dialing signal for automatically outputting conventional dialing pulses on the subscribers telephone lines for performing the dialing function.

28. A cordless telephone comprising a full duplex two-way radio link including a base unit coupled to a subscriber'"'"'s telephone lines and a cordless remote unit, said base unit including an antenna, a transmitter and a receiver and said remote unit including an antenna, a transmitter and a receiver, the transmitter of said base unit operating at a first non-CB frequency to be received by the receiver of said remote unit and the transmitter of said remote unit operating at a second different and distinct non-CB frequency to be received by the receiver of said base unit, both said base unit and said remote unit including means for coupling a portion of the transmitted signal into the receiver of the corresponding unit for providing the local oscillator function for said corresponding receiver while simultaneously enabling the use of a single antenna in each of said base unit and said remote unit without undue interference between the transmitted and received signals, said remote unit including a cordless handset, means for indicating an "off-the-hook" condition for said handset, means for entering a security identification code, and means responsive to an indication of said "off-the-hook" condition for transmitting a security identification code to said base unit, said base unit including means responsive to the receipt of said security identification code for identifying an authorized user and seizing said telephone lines in response thereto to enable two-way communications between the authorized user of the cordless handset of the remote unit and the party calling or being called on the telephone lines.

29. The cordless telephone of claim 28 wherein said coupling means of each of said base unit and said remote unit includes a first crystal filter operatively connected between said transmitter and said antenna, a second crystal filter operatively connected between said antenna and said receiver, and means connected between said first and second crystal filters for passing a portion of said transmitted signal into said receiver to provide the required local oscillator function of the corresponding receiver.

30. The cordless telephone of claim 28 wherein said means for entering a security identification code includes a plurality of manually-operable switches, said means for transmitting includes means responsive to the position of said plurality of manually-operable switches for defining a security identification code data word, means responsive to an "off-the-hook" indication for generating a subcarrier frequency tone, and means responsive to said generated subcarrier frequency tone for FSK-encoding said security identification code data word for transmission to said base unit, wherein said means responsive to the receipt of said security identification code includes means responsive to said transmitted FSK-encoded security identification code data word for decoding same and generating a digital security code indicative thereof, means for storing an authorized security identification code data word, means responsive to a comparison of said digital security code and said stored authorized security code data word for generating a command signal whenever an authorized user is detected, and means responsive to said command signal for seizing said telephone lines and maintaining the acquisition thereof so long as said base unit continues to receive the subcarrier frequency tone transmitted from said cordless remote unit.

31. A cordless telephone comprising a full duplex two-way radio link including a base unit coupled to a subscriber'"'"'s telephone lines and a cordless remote unit, said base unit including an antenna, a transmitter and a receiver, and said remote unit including an antenna, a transmitter and the receiver, the transmitter of said base unit operating on a first non-CB frequency to be received by the receiver of the remote unit and the transmitter of said remote unit operating at a second different and distinct non-CB frequency to be received by the receiver of the base unit, each of said base unit and said remote unit including means for coupling a portion of the transmitter signal into the receiver of a corresponding unit for providing the local oscillator function thereof while simultaneously enabling the use of a single antenna in each of said base unit and said remote unit without undue interference between the transmitted and received signals, said remote unit further including a cordless handset, means for entering a security identification code, means for indicating an "off-the-hook" condition for said handset and means responsive to an indication of said "off-the-hook" condition for transmitting a security identification code to said base unit, said base unit further including means responsive to the receipt of said security identification code for identifying an authorized user and seizing said telephone lines in response thereto to enable two-way communications between the authorized user at the cordless handset of the remote unit and the party calling or being called on the telephone lines.

32. The cordless telephone of claim 31 wherein each of said base unit and said remote unit includes means for establishing a receive-only mode of operation and means for establishing a transmit-receive mode of operation, said coupling means includes first and second signal paths operatively connected between the transmitter output and a corresponding receiver input, said first signal path including a first crystal filter operatively connected between the output of the transmitter and the single antenna, a second crystal filter operatively coupled between said single antenna and the input of a corresponding receiver, the band pass characteristics of said first and second crystal filters being such that only a relatively small portion of the transmitter signal is passed by said second filter to the receiver input for providing the local oscillator function thereof during said transmit-receive mode of operation, said coupling means further including a second path connected directly across said first and second crystal filters from the transmitter output to the receiver input for injecting a relatively small transmitter signal into the receiver for providing the local oscillator function thereof during said receive-only mode of operation.

33. The cordless telephone of claim 32 wherein the transmitter of each of said base unit and said remote unit further includes means for normally driving the transmitter with a relatively weak current during said receive-only mode of operation for generating a relatively weak transmitter signal of insufficient strength to pass over said first signal path but sufficient to pass said second path to provide the local oscillator function of the receiver, and further including means responsive to said transmit-receive mode of operation for disabling said second path and driving said transmitter hard to generate a relatively strong transmitter signal of sufficient strength that a relatively small portion is passed by said second filter to provide the local oscillator function of the receiver during transmit-receive operations.

34. The cordless telephone of claim 33 wherein the transmitter of said base unit and said remote unit each include a transmitter oscillator and means for normally biasing said transmitter oscillator to generate a relatively weak transmitter signal at the output thereof during the receive-only mode of operation, each of said transmitters further including means responsive to the transmit-receive mode of operation for applying a greater current to the transmitter oscillator to produce a relatively strong transmitter signal, said second path further including a switching element coupled between said second path and ground and responsive to said transmit-receive mode of operation for enabling the switching element to establish a conductive path to ground to disabling said second path while said first path passes a relatively small portin of the transmitter signal to the receiver input for providing the local oscillator function thereof.

35. The cordless telephone of claim 31 wherein said means for transmitting a security identification code includes a plurality of manually-operable switches, means responsive to the position of said plurality of manually-operable switches for defining a security identification code data word, means responsive to an "off-the-hook" indication for generating a subcarrier frequency tone for FSK-encoding said security identification data word for transmission to said base unit, wherein said means responsive to the receipt of said security identification code includes means responsive to said transmitted FSK-encoded security identification code data word for decoding same and generating a digital security code data word indicative thereof, means for storing an authorized security identification code word, means responsive to a comparison of said decoded digital security code data word and said stored authorized security identification code word for generating a command signal when an authorized user is detected, and means responsive to said command signal for seizing said telephone lines and maintaining the acquisition thereof so long as said base unit continues to receive the subcarrier frequency tone transmitted from said cordless remote unit.

36. A cordless telephone comprising a base unit operatively coupled to a subscriber'"'"'s telephone lines and a portable cordless handset, said portable cordless handset including a microphone into which the user speaks for generating a microphone-produced audio signal, a speaker for outputting a ringing tone signal and audible speech, a first transceiver for transmitting an RF carrier frequency-modulated with audio signals and data words to said base unit for and for receiving a local ringing signal generated by said base unit and audio speech signals from said telephone lines, said first transceiver feeding said local ringing signal and said speech signals to said speaker for audiblizing same, means for generating a discrete security identification code data word indicative of the user'"'"'s identification, hook switch means having a first position representing a condition such as normally exists when a telephone is "hung-up" and a second position representing that condition normally existing when a telephone is "off-the-hook" and means responsive to said hook switch means being in said second position for coupling said generated security code data word to said first transceiver for transmission to said base unit, said base unit including a second transceiver means for transmitting a local ringing signal and audio speech signals to said cordless handset, said audio speech signals originally being transmitted over said telephone lines to said base unit and for receiving said microphone-produced audio signals and data words transmitted by said cordless handset, means for storing a discrete security code identifying an authorized user, microprocessor means for receiving said security code data word from said cordless handset and comparing same with said stored discrete security code to generate a line seizure command whenever an authorized user is identified, and means responsive to a line seizure command for seizing the telephone lines and maintaining the acquisition thereof as long as the previously identified user maintains said hook switch means in said second position, said base unit further including means for detecting an in-coming ringing signal on said telephone lines and generating a ring detection signal in response thereto, said microprocessor means including means responsive to said ring detection signal for generating a local ringing signal and a transmit enable signal, said base unit further including a transmitter, a receiver, and a transmit enable switching means having a first switch state which allows a substantially reduced amount of power to be supplied to said base unit transmitter during the receive-only mode of operation since substantially reduced amount of power being sufficient to provide only that amount of transmitter signals necessary to provide adequate mixing operation in the base unit receiver by providing the local oscillator function thereof, and a second switch state for enabling full power to be applied to said base unit transmitter for enabling full transmitter and receiver operations during the transmit-receive mode of operation, said transmit enable switching means being responsive to said transmit enable signal from said microprocessor means for switching to said second state in response to the detection of a ringing signal and powering the base unit transmitter to enable the base unit to transmit the microprocessor-produced local ringing signal to said cordless handset.

37. The cordless telephone of claim 36 wherein said microprocessor means further includes means for detectng the receipt of a data word from said cordless handset and means for generating a muting command during identification and dialing operations and wherein said base unit further includes means responsive to said muting command from said microprocessor means for temporarily disabling transmitter operations.

38. The cordless telephone of claim 36 wherein said cordless handset further includes a keyboard means for manually entering keyboard information and logic means for generating a keyboard-defined dialing code data word, said data word being transmitted by said first transceiver means of said cordless handset to said base unit, said microprocessor means further including means responsive to said dialing code data words for generating dialing commands, said base unit including means responsive to said dialing commands for outputting dialing signals representing a selected telephone number over the subscriber'"'"'s telephone lines for conventional dialing purposes.

39. The cordless telephone of claim 38 wherein said outputting means responsive to said microprocessor-generated dialing commands includes touch tone encoder means responsive to said dialing commands for generating dual tone multiple frequency dialing signals for transmission over said telephone lines.

40. The cordless telephone of claim 38 wherein said base unit includes dialing rate switching means for selecting one of a first and second state, means responsive to said first state for generating a sequence of dialing pulses at a rate of 10 pulses per second for outputting said dialing signals and means responsive to said second state for generating a sequence of digital dialing pulses at a rate of 20 pulses per second for outputting said dialing signals.

41. The cordless telephone of claim 38 wherein said base unit further includes a dial selection switching means for selecting one of a first, second and third state, said outputting means including means responsive to said first state for generating a sequence of digital dialing pulses indicative of a dialing command at a first rate for output over the telephone lines, means responsive to said second state for generating a sequence of digital dialing pulses indicative of a dialing command at a second rate for output over said telephone lines where said second rate is greater than said first rate, and tone-encoder means responsive to said third state for generating dual tone multiple frequency dialing signals indicative of a dialing command for output over said telephone lines.

42. The cordless telephone of claim 38 wherein said cordless handset further includes a keyboard for entering dialing codes and the like and wherein hook switch means is disposed on said keyboard to enable the user of said cordless handset to more easily establish an "off-the-hook" condition for activating said hook switch means to indicate that he has picked up the telephone to answer an in-coming call or to place an out-going call.

43. The cordless telephone of claim 36 wherein said cordless handset further includes the keyboard for manually entering numeric and command information and logic means for generating keyboard-defined data words which are transmitted to said base unit via said first transceiver means of said cordless handset, said microprocessor means including memory means for storing at least one dialing code data word indicative of a predetermined telephone number, means responsive to the receive of a keyboard-defined data word for addressing said memory means and recalling said dialing code data word and means responsive to said recalled dialing code data word for generating telephone dialing signals corresponding thereto.

44. The cordless telephone of claim 36 wherein said means for generating a discrete security code data word in said cordless handset includes logic means for generating a subcarrier frequency pilot tone and means responsive to said pilot tone and said data word for generating an FSK-encoded equivalent of said data word for transmission to said base unit via said first transceiver means, said base unit further including means for decoding said FSK-encoded data word, said microprocessor means including means responsive to said data word for comparing same with said stored discrete security code and generating said line seizure command when an authorized user is identified.

45. The cordless telephone of claim 44 wherein said cordless handset further includes a keyboard, logic means for generating keyboard-defined dialing code data words, said FSK-encoding means being responsive to said dialing code data words for encoding same for transmission to said base unit and the FSK-decoder means of said base unit being responsive to said FSK-encoded dialing code data words for decoding same for transmission to said microprocessor means, said microprocessor means including means responsive to said decoded dialing code data words for enabling conventional dialing signals to be outputted on said subscriber'"'"'s telephone lines.

46. The cordless telephone of claim 36 wherein said means for storing a discrete security code identifying an authorized user includes a plurality of manually operable switches, means responsive to said plurality of manually operable switches for generating said discrete security code and means for temporarily storing said generated discrete security code for comparison purposes.

47. The cordless telephone of claim 44 wherein the continued generation of the subcarrier frequency pilot tone is maintained as long as said hook switch means is in said "off-the-hook" position, said microprocessor means being responsive to the continued receipt of said pilot tone after the initial seizure of said subscriber'"'"'s telephone lines for maintaining the acquisition thereof after the initial seizure until a predetermined time after the hook switch is activated to prevent an inadvertent call termination due to the presence of noise or the like.

48. A cordless telephone comprising a base unit operatively coupled to a subscriber'"'"'s telephone lines and a portable cordless handset, said portable cordless handset including a microphone into which the user speaks for generating a microphone-produced audio signal, a speaker for outputting a ringing tone signal and audible speech, a first transceiver for transmitting an RF carrier frequency-modulated with audio signals and data words to said base unit for and for receiving a local ringing signal generated by said base unit and audio speech signals from said telephone lines, said first transceiver feeding said local ringing signal and said speech signals to said speaker for audiblizing same, means for generating a discrete security identification code data word indicative of the user'"'"'s identification, hook switch means having a first position representing a condition such as normally exists when a telephone is "hung up" and a second position representing that condition normally existing when a telephone is "off-the-hook" and means responsive to said hook switch means being in said second position for coupling said generated security code data word to said first transceiver for transmission to said base unit, said base unit including a second transceiver means for transmitting a local ringing signal and audio speech signals to said cordless handset, said audio speech signals originally being transmitted over said telephone lines to said base unit and for receiving said microphone-produced audio signals and data words transmitted by said cordless handset, means for storing a discrete security code identifying an authorized user, microprocessor means for receiving said security code data word from said cordless handset and comparing same with said stored discrete security code to generate a line seizure command whenever an authorized user is identified, and means responsive to a line seizure command for seizing the telephone lines and maintaining the acquisition thereof as long as the previously identified user maintains said hook switch means in said second position, said transceiver means of both the cordless handset and the base unit each including a transmitter means, an antenna, and a receiver means, said transceiver means enabling a full duplex two-way FM radio transmission between said base unit and said cordless handset, the transmitter means of said cordless handset and receiver means of said base unit operating on a first non-CB frequency and the transmitter means of said base unit and the receiver means of said cordless handset operating on a second different and distinct non-CB frequency and circuit means whereby at least a portion of the transmitter frequency of each of said transmitter means is injected into the receiver input for serving as the local oscillator frequency of the corresponding receiver means thereby enabling transmission and reception upon the same antenna on each of said first and second transceiver means while substantially eliminating undesirable interference between transmitted and received signals.

49. The cordless telephone of claim 48 wherein said first and second non-CB frequencies are in the range 49.82 Mhz≦

f≦

49.90 Mhz.

50. The cordless telephone of claim 49 wherein said first and second non-CB frequencies are separated by a frequency of 15 nKHz where "n" is a whole number and 1≦

n≦

4.

51. The cordless telephone of claim 48 wherein each of said first and second transceiver circuit means includes a first crystal filter for passing only the transmitter frequency signals from its transmitter means to the corresponding antenna, a second crystal filter for passing substantially only the receiver frequency signals from said antenna to the input of the corresponding receiver means, said means coupling said first and second crystal filters for supplying a portion of the transmitter signal to the input of a corresponding receiver means for performing the local oscillator function during the transmit-receive mode of operation, said first and second crystal filters having band pass characteristics which insure that only a small portion of the transmitter signal is supplied to the input of the receiver for performing the local oscillator function, said filter also serving to reduce the transmitted power level available to the receiver input while simultaneously providing high receiver selectability.

52. The cordless telephone handset of claim 51 wherein each of said transmitter means includes a transmitter oscillator, means for normally biasing said transmitter oscillator so that only a relatively weak transmitter frequency signal is generated during the receive-only mode of operation, said first and second crystal filters operatively coupling the output of the transmitter oscillator with the corresponding receiver input such that none of the relatively weak transmitter oscillator signal is coupled to the receiver input during the receive-only mode of operation, said circuit means including signal injection means directly coupling the output of the transmitter oscillator to the receiver input for supplying said relatively weak transmitter frequency signal to the input of a corresponding receiver to provide to the local oscillator function thereof during receive-only operations, means responsive to the transmit receive-only mode of operation for disabling the signal injection path and supplying greater power to said transmitter oscillator to provide a relatively strong transmitter output required for driving the antenna and insuring that at least a small portion of the transmitter signal is passed by the second crystal filter to the receiver input to provide the local oscillator function thereof during transmit receive operations.

53. A cordless telephone comprising a base unit operatively coupled to a user'"'"'s telephone lines and a portable cordless handset, each of said base unit and said cordless handset including a transceiver having a transmitter, a receiver and a single antenna for forming a full duplex radio link for two-way communication between said base unit and said cordless handset, the transmitter of said base unit and the receiver of said cordless handset operating on a first non-CB frequency and the transmitter of said cordless handset and the receiver of said base unit operating on a second different and distinct non-CB frequency, each of said transceivers further including means for selecting one of a receive-only mode of operation and a transmit-receive mode of operation, said cordless telephone further comprising:

means responsive to the selection of said receive-only mode of operation for supplying a relatively small quantity of energy to said transmitter for generating only a relatively weak transmitter frequency signal;

signal injection means for directly injecting said relatively weak transmitter frequency signal into the input of a corresponding receiver to serve as the local oscillator frequency thereof;

means responsive to the selection of said transmit-receive mode of operation for supplying a relatively large quantity of energy to said transmitter for generating a relatively strong transmitter frequency signal for driving said antenna while simultaneously disabling said direct signal injection means; and

means for operatively coupling the single antenna of each of said transceivers to a corresponding transmitter output and to a corresponding receiver input such that when said transceiver is in said transmit-receive mode of operation, at least a portion of said relatively strong transmitter frequency signal is supplied from the transmitter output to a corresponding receiver input for providing the local oscillator function thereof, thereby enabling at least some portion of said transmitter signal to be supplied to the input of a corresponding receiver for providing the local oscillator frequency thereof regardless of whether said transceiver is operating in said receive-only mode of operation or in said transmit-receive mode of operation.

54. The cordless telephone of claim 53 wherein said transceivers are frequency modulated and wherein said first and second non-CB frequencies are in the range 49.82 MHz≦

f≦

49.90 MHz.

55. The cordless telephone of claim 53 wherein said first non-CB frequency is greater than said second non-CB frequency.

56. The cordless telephone of claim 53 wherein said first and second non-frequencies are separated by a small fractional percentage of said first frequency.

57. The cordless telephone of claim 56 wherein said small fractional percentage difference between said first and second non-CB frequencies is preferably 5n Khz where "n" is a whole number and 1≦

f≦

4.

58. The cordless telephone of claim 53 wherein each of said transmitters includes a transmitter output and where in each of said receivers includes an input, and wherein each of said antenna coupling means includes a first crystal filter operatively coupled between the transmitter output and said antenna for passing the relatively strong transmitter frequency signal from the transmitter output to the antenna, a second crystal filter operatively coupled between the antenna and the receiver input for passing receiver frequency signals from the antenna to the input of said receiver, the band-pass characteristics of said first and second crystal filters being such that said second crystal filter normally rejects most of the relatively strong transmitter frequency signal but passes a small portion thereof to the input of said receiver for performing said local oscillator function whenever said transceiver is operating in said transmit-receive mode of operation.

59. The cordless telephone of claim 58 wherein each of said transmitters includes a transmitter oscillator and wherein said direct signal injection means includes a direct circuit path for normally coupling the output of the transmitter oscillator to the input of a corresponding receiver for directly injecting said normally-generated relatively weak transmitter frequency signal into said receiver to serve as the local oscillator frequency thereof whenever said transmitter is operated in said receive-only mode of operation, and wherein said disabling means includes the normally non-conductive switching means between said circuit path and ground and responsive to the selection of said transmit-receive mode of operation for switching to a conductive state to ground said circuit path and decouple said direct signal injection means to prevent direct local oscillator injection while the transmitter is in said transmit-receive mode of operation.

60. The cordless telephone of claim 53 wherein said cordless handset further includes keyboard means for entering dialing information, logic means responsive to keyboard-entered dialing information for generating a dialing data word indicative thereof and means for coupling said dialing data word to said transmitter for transmitting same to said base unit, and wherein said base unit further includes means responsive to the receipt of said dialing data word for generating a sequence of dialing pulses for transmission over said telephone lines to perform the dialing function and a second switching means for selecting one of a first and second output rate at which said sequence of dialing pulses are to be transmitted over said telephone lines.

61. The cordless telephone of claim 60 wherein said second switching means includes means for selectively outputting a digital dialing pulse at a first output rate of 10 pulses per second and for selectively outputting digital dialing pulses at a second output rate of 10 pulses per second.

62. The cordless telephone of claim 53 wherein said cordless handset further includes keyboard means for entering dialing information, logic means responsive to keyboard-entered dialing information for generating dialing data words indicative thereof and means for coupling said dialing data words to said transmitter for transmission to said base unit, and wherein said base unit further includes means responsive to the receipt of said dialing data words for generating dialing commands corresponding thereto, dial selection switching means for selecting one of a first switch position for generating a first switch signal, a second switch position for generating a second switch signal, and the third switch position for generating a third switch signal, means responsive to said first switch signal for generating a sequence of digital dialing pulses corresponding to said dialing commands at a rate of 10 pulses per second, means responsive to said second switching signal for generating a sequence of digital dialing pulses corresponding to said dialing commands at a rate of 20 pulses per second, means responsive to said third switching signal for generating a dual tone multiple frequency dialing signal corresponding to said dialing commands and means for coupling said digital dialing pulses and said dual tone multiple frequency dialing signals to said telephone lines for transmission thereover.

63. The cordless telephone of claim 53 wherein said cordless handset includes keyboard means for entering dialing information, second switching means for entering security code information, logic means responsive to said dialing information and said security code information for generating data words indicative thereof for transmission to said base unit, means responsive to the receipt of a local ringing signal transmitted from said base unit for indicating an in-coming call, hook switch means responsive to a user going "off-the-hook" for generating a transmit-receive signal indicative thereof, means responsive to said transmit-receive signal for transmitting said data words to said base unit, and wherein said base unit further includes means responsive to the receipt of a transmitted data word indicative of dialing information for generating a dialing command corresponding thereto, means responsive to a transmitted data word indicative of security code information for generating a security code identification command corresponding thereto, means for storing a predetermined security code identifying an authorized user, means responsive to an in-coming ringing signal on said telephone lines for generating a local ringing signal for transmission to said cordless handset, means responsive to a security code identification data command for comparing same with the stored security code and generating a transmit-enable command in response to the identification of an authorized user, means responsive to said transmit-enable command for selecting said transmit-receive mode of operation, means responsive to predetermined signals received from said cordless handset for seizing and maintaining said user'"'"'s telephone lines to establish two-way communications between the party on the telephone and the authorized user of the cordless handset, means responsive to said dialing command for generating dialing signals for transmission over said seized telephone lines to perform the dialing function.

64. The cordless telephone of claim 63 wherein said logic means includes FSK-encoding means responsive to said data words for generating an FSK-encoded equivalent thereof and means for supplying said FSK-encoded data words to the transmitter of said cordless handset for transmission to said base unit, and wherein said base unit further includes FSK-decoder means responsive to the receipt of an FSK-encoded data word transmitted by said cordless handset for decoding same to reconstruct said data word for generating said dialing commands and security code commands.

65. The remote cordless telephone of claim 64 wherein said base unit further includes a dialing mode switching means having a first switch position for selectively outputting a sequence of dialing impulses indicative of said dialing command at the rate of 10 pulses per second over said telephone lines, a second switch position for selectively outputting a sequence of digital dialing pulses indicative of said dialing command at a rate of 20 pulses per second over said telephone lines, and a third switch position for selectively outputting a sequence of dual tone multiple frequency dialing signals over said telephone lines, thereby enabling said remote cordless telephone system to be used with any type of telephone system in commercial use today.

66. The cordless telephone of claim 53 wherein said cordless handset includes keyboard means for entering dialing information, second switching means for entering security code information, logic means responsive to said dialing information and said security code information for generating data words indicative thereof, FSK-encoding means responsive to said data words for generating an FSK-encoded equivalent thereof for transmission to said base unit, and wherein said base unit includes FSK-decoder means for decoding said transmitted FSK-encoded data words and regenerating the dialing information and security code information, said base unit further including a microprocessor means including means responsive to a data word indicative of dialing information for generating a dialing command, means responsive to a data word indicative of security code information for generating a security code identification command, means for storing a predetermined security code identifying an authorized user, means responsive to an in-coming ringing signal on said telephone lines for generating a local ringing signal for transmission to said cordless handset, means responsive to a security code identification command for comparing same with said stored security code and generating a transmit-enable command in response to the identification of an authorized user, means responsive to said transmit-enable command for seizing and maintaining said telephone lines to enable two-way communications between the party on the telephone and the authorized user, and means responsive to said dialing commands for generating dialing signals for transmission on said seized telephone lines to perform the conventional dialing function.

67. The cordless telephone of claim 66 wherein said base unit further includes dialing mode switching means having a first position for selectively outputting the sequence of dialing signals at a rate of 10 pulses per second over said seized telephone lines, a second switch position for selectively outputting a sequence of digital dialing signals at the rate of 20 pulses per second over said seized telephone lines, and a third switch position for selectively outputting a sequence of dual tone multiple frequency dialing signals over said seized telephone lines thereby enabling said cordless telephone system to be used with any type of telephone system in commercial use today.

68. The cordless telephone of claim 53 wherein said base unit further includes transformer means for coupling the base unit transceiver to the user'"'"'s telephone lines, said user'"'"'s telephone lines including a tip line and a ring line, said base unit also including means for generating a line seizure command, said transformer coupling means including a line seizure relay means having a normally de-energized relay coil and a normally open receive-only switch, said transformer having a primary coil and a secondary coil, said primary coil and said normally open relay-operated switch being connected in series to join said tip and ring lines, said line seizure relay means being responsive to the generation of said line seizure command for energizing said relay coil to close said relay operated switch for seizing the telephone lines, said base unit also including input amplifier means coupled to the secondary coil for inductively coupling signals from the seized telephone lines to the input of the transmitter and output amplifier means inductively coupled to the secondary coil for outputting audio signals and dialing signals from the receive to the seized telephone lines.

69. The cordless telephone of claim 68 wherein said portable cordless handset includes keyboard means for generating dialing data words, means for entering security identification code data words, means for generating a pilot tone, means for FSK-encoding said data words utilizing said pilot tone for transmission to said base unit, said base unit including means responsive to the receipt of said FSK-encoded data words for decoding same, means for storing a security code indicative of an authorized user, means for comparing a decoded security identification data word with said stored security word for identifying an authorized user, means responsive to the identification of an authorized user for generating a transmit-enable command and said line seizure command, said means for generating said line seizure command being responsive to the continued receipt of said pilot tone from said cordless handset for maintaining line acquisition so long as said cordless handset is off the hook.

70. The cordless telephone of claim 53 wherein said base unit includes means responsive to the receipt of an in-coming ringing signal on said telephone lines for generating a local ringing signal for transmission to said cordless handset, wherein said cordless handset includes a speaker, an audio amplifier for driving said speaker, said audio amplifier including positive and negative inputs at an output operatively coupled to drive said speaker, a summing node at said negative input, first resistive means normally coupling a relatively low receive-only signal to said negative input when said switching means has selected said receive-only mode of operation for said transceiver and for coupling a relatively high transmit-receive signal to said negative input whenever said switching means has selected said transmit-receive mode of operation, said receiver having a demodulation output for outputting an audio signal whenever an audio input signal is transmitted to said receiver, second resistive means for coupling the audio signal from the demodulation output of said receiver to said summing node, means associated with said receiver for normally supplying a relatively high input signal to the positive input but responsive to the receipt of said local ringing signal for supplying a relatively low input signal to said positive input, a normally-closed switching means disposed in a portion of said receiver, third resistive means coupling said normally closed switching means to said summing node for forming a resistive voltage divider network to normally reduce the voltage level at said summing node unless said normally-closed switching means is open, said normally-closed switching means being responsive to the receipt of said local ringing signal for opening to disable said resistive voltage divider network to allow the full undivided strength of the local ringing signal to be applied to said summing node, said audio amplifier being (1) responsive to a relatively low voltage at said positive input indicative of the receipt of a local ringing signal and the relatively low voltage at the negative input indicative of a receive-only mode of operation for applying the full undivided strength of the local ringing signal to drive said speaker so as to produce a relatively loud audible ringing sound, (2) responsive to a relatively high voltage at the positive input indicative of the absence of said local ringing signal and the relatively high voltage at said negative input indicative of a transmit-receive mode of operation for applying the voltage-divided audio signal indicative of in-coming speech to drive said speaker to produce normally audible speech signals, (3) responsive to a relatively low signal at the positive input indicative of the receipt of a local ringing signal and a relatively high signal at the negative input indicative of a transmit-receive mode of operation for off-setting said audio amplifier out of its operating range low so as to prevent the operation thereof whenever a local ringing signal is received after the telephone is off the hook for initiating or answering a call or the like, and (4) responsive to a relatively high signal at the positive input indicating the absence of a local ringing signal and a relatively low signal at the negative input indicating a receive-only mode of operation for off-setting the audio amplifier out of its operating range high to prevent speaker operation before the telephone has rung and been answered.

71. The cordless telephone of claim 70 wherein said input amplifier means and said output amplifier means include feedback means between the output of said input amplifier in the input of said output amplifier for cancelling out the transmitter modulated signal via circuit means for enabling sufficient phase adjustment and amplitude cancellation.

72. In a two-way cordless telephone system including a base unit coupled to a subscriber'"'"'s telephone lines and a remote cordless handset, said base unit having an FM radio transceiver for transmitting and receiving radio signals to and from said cordless handset, means coupled to said telephone lines for detecting an in-coming ringing signal and generating a ring detection signal in response thereto, means for normally supplying a relatively small amount of energy to said radio transceiver sufficient to maintain receiver operation, first switching means responsive to a transmit-receive command for supplying a relatively large amount of energy to the transceiver for operating both the transmitter and receiver portions thereof, means for storing the predetermined authorized user'"'"'s identification code, means responsive to a line seizure command for completing a circuit to said telephone lines to enable two-way communications thereover, means responsive to dialing commands for outputting dialing signals to said telephone lines for performing the conventional dialing functions, and said remote cordless handset having an FM radio transceiver for transmitting and receiving radio signals to and from said base unit, a second switching means for defining an "in use" condition, third switching means for manually entering a user'"'"'s security identification code, means responsive to said second switching means defining said "in use" condition and to said security identification code entered by said third switching means for transmitting the security identification data word to said base unit, a key pad for entering dialing information, means responsive to said key pad-entered information for transmitting dialing information data words indicative of a desired telephone number to be dialed to said base unit, the improvement comprising:

microprocessor means disposed in said base unit (1) responsive to said ring detection signal for generating said transmit-receive command and a local ringing signal for transmission to said remote cordless handset;

(2) responsive to the receipt of a security identification code data word for comparing same with said stored predetermined authorized user'"'"'s identification code for generating said line seizure command whenever an authorized user is detected;

(3) responsive to the receipt of a dialing information data word for generating dialing commands corresponding thereto; and

(4) for storing at least one dialed telephone number for subsequent recall to automatically generate said dialing commands to initiate the automatic redialing of said stored telephone number without the necessity of entering a complete telephone number on said key pad, and

both the FM radio transceiver of said base unit and the FM radio transceiver of said cordless handset including a transmitter, a receiver, and an antenna, the base unit transmitter and the handset receiver operating on a first non-CB frequency and the handset transmitter and base unit receiver operating on a second different and distinct non-CB frequency, each of said transmitters including a transmitter oscillator stage, means for normally supplying a relatively small amount of energy, indicative of a receive-only mode of operation, to said transmitter oscillator for generating a relatively weak transmitter signal but responsive to said transmit-receive mode of operation for supplying a relatively large amount of energy to said transmitter oscillator stage to generate a relatively strong transmitter signal for driving said antenna, the transceiver of each of said base unit and said remote cordless handset including first and second signal injection paths operatively coupled between the transmitter output and a corresponding receiver input, said first signal injection path including a first crystal filter operatively connected between the transmitter output and said antenna, a second crystal filter operatively coupled between said antenna and the receiver input, the band pass characteristics of said first and second crystal filters being such that only a relatively small portion of the transmitter signal is passed to the receiver during the transmit-receive mode of operation for providing the local oscillator function of the receiver and said second signal injection path includes a direct electrical path operatively connected between the transmitter output and the receiver input and a switching element operatively coupled in the path for disabling same during the transmit-receive mode of operation, said second signal injection path being conductive during the receive-only mode of operation for supplying the relatively weak transmitter oscillator signal directly into the receiver for providing the local oscillator function thereof.

73. The improved cordless telephone system of claim 72 wherein said remote cordless handset incudes means responsive to said "in use" condition for generating a pilot tone, means responsive to said pilot tone signal for FSK-encoding said data words prior to transmission to said base unit, and said base unit further includes FSK-decoder means responsive to the receipt of said FSK-encoded data words for decoding same and supplying digital equivalents thereof to said microprocessor means for subsequent processing.

74. The improved cordless telephone system of claim 72 wherein said means for outputting dialing signals comprises dialing output switching means for selecting first, second and third dialing output states, means responsive to said first state and said dialing commands for generating a sequence of digital dialing pulses indicative of the number to be dialed for output on said telephone lines at a rate of 10 pulses per second, means responsive to said second state and said dialing commands for generating a sequence of digital dialing pulses indicative of the number to be dialed for output on said telephone lines at a rate of 20 pulses per second, and dual tone multiple frequency tone generator means responsive to said third state and said dialing commands for generating a dual tone multiple frequency dialing signal indicative of the number to be dialed for output on said telephone lines.