Telephone line carrier system

• US 4,807,225 A
• Filed: 02/02/1987
• Issued: 02/21/1989
• Est. Priority Date: 02/02/1987
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.), AT&T Information Systems Inc. (AT&T, Inc.)
• Original Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Inventors: Fitch, Richard C.
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US07/010,248
• Time in Patent Office: 750 Days
• Field of Search: 370/71, 370/72, 370/73, 370/76, 370/69.1, 370/124
• US Class Current: 370/295
• CPC Class Codes: H04M 9/027 Frequency division multiplex systems

Abstract

A telephone line carrier system comprising a master station (221) and one or more remote stations (222) is disclosed. Each station (221, 222) is bridged, in a parallel electrical connection, onto a wire-pair (201) that extends from the station to a telephone line switching system. Each station (221, 222) includes a line interface (110, 310) for connecting to the wire-pair (201) at voiceband frequencies, and a radio frequency interface (700, 800) for connecting to the wire-pair (201) at Radio Frequencies (RF). Each station further includes multiplexer and demultiplexer equipment (500, 600) for frequency shifting voice and data channels between baseband and RF. Frequency modulation and full duplex transmission are used for voice communication while amplitude modulation and half-duplex transmission are used for data communication. The master station (221) terminates a second telephone line (202) and frequency multiplexes/demultiplexes signals between the second telephone line (202) and the wire-pair (201) thereby providing remote stations with access to the second line. Telephone status and control information, including ringing and answer control, are exchanged between controllers (160, 360) via the data channel.

Claims

1. Telephone station apparatus for use at a subscriber'"'"'s premises, adapted to be parallel connected onto a first wire-pair that extends between said premises and a telephone line switching system, the apparatus including means for transmitting and receiving electrical signals substantially in a frequency band below 4 kHz,

CHARACTERIZED BY:

a first modulator, having input and output ports, responsive to the transmitting means for converting electrical signals at its input port and in the frequency band below 4 kHz into electrical signals in a first frequency band above 4 kHz at its output port;

means interconnecting the output port of the first modulator with the first wire-pair;

a first demodulator, having an input port connected to the first wire-pair, for converting signals at its input port and in a second frequency band above 4 kHz into electrical signals in the frequency band below 4 kHz at an output port thereof;

means interconnecting the output port of the first demodulator with the receiving means;

means responsive to one or more telephone station control signals or status indicators for encoding same into a digital data signal;

a second mdoualtor, having input and output ports, responsive to the digital data signal at its input port for converting same into an electrical signal in a third frequency band above 4 kHz at its output port; and

means interconnecting the output port of the second modulator with the first wire-pair, whereby additional channels are added to an existing wire-pair without interference with, or displacement of, voiceband services already present on the wire-pair.

2. The telephone station apparatus of claim 1 wherein said first modulator frequency modulates a carrier signal in the first frequency band in proportion to the magnitude of the electrical signal at its input port, and wherein the first demodulator frequency demodulator electrical signals received at its input port in the second frequency band above 4 kHz.

3. The telephone station apparatus of claim 1 further adapted to terminate a second wire-pair that extends between the subscriber'"'"'s premises and the telephone line switching system, FURTHER CHARACTERIZED BY switching means, interconnecting electrical signals on the second wire-pair with the input port of the first modulator, and interconnecting electrical signals at the output port of the first demodulator with the second wire-pair, whereby a communication link between the first and second wire-pairs is established.

4. The telephone station apparatus of claim 1 further including a controller interconnected with, and responsive to the electrical state of, a plurality of switch contacts on a front panel of the telephone station apparatus for generating the digital data signal, said digital data signal being encoded to contain an indication of the electrical state of one or more of the switch contacts.

5. The telephone station apparatus of claim 1 wherein said second modulator amplitude modualtes a carrier signal in the third frequency band in accordance with the magnitude of the digital data signal at its input port, said telephone station apparatus further including a second demodulator, having input and output ports, for amplitude demodulating electrical signals in the third frequency band received at its input port, whereby half duplex data communication service is provided.

6. The telephone station apparatus of claim 4 wherein the digital data signal is binary, and the carrier signal of the second modulator is switched off and on in response to the magnitude of the binary signal.

7. The telephone station apparatus of claim 6 wherein the information content of the binary signal is contained in the line duration of each binary pulse.

8. Carrier communication apparatus adapted to be bridged onto a telephone wire-pair, the apparatus including microphone and loudspeaker transducers for converting audible sounds into voiceband electrical signals, a first modulator for converting the voiceband electrical signals from the microphone transducer into a first frequency band above 4 kHz, and a first demodulator for converting modulated signals in a second frequency band above 4 kHz into voiceband electrical signals for interconnection with the loudspeaker transducer,

CHARACTERIZED BY:

hybrid circuit means for interconnecting voiceband signals between the wire-pair and said microphone and loudspeaker transducers;

means responsive to one or more carrier communication apparatus control signals or status indicators for encoding same into digital data signals;

a second demodulator having input and output ports, responsive to the digital data signals at its input port for converting same into electrical signals in a third frequency band above 4 kHz at its output port; and

means interconnecting the output port of the second modulator with the wire-pair.

9. The carrier communication apparatus of claim 8 further including a controller interconnected with, and responsive to the electrical state of, a plurality of switch contacts on a front panel of the carrier communication apparatus for generating the digital data signal, said digital data signal being encoded to contain an indication of the electrical state of one or more of said switch contacts.

10. The carrier communication apparatus of claim 8 wherein said first modulator frequency modulates a carrier signal in accordance with the magnitude of the voiceband electrical signals from the microphone, and wherein the first demodulator frequency demodulates electrical signals in the second frequency band, whereby frequency modulation and demodulation provide high quality, full duplex voice communications.

11. The carrier communication apparatus of claim 8, further adapted to terminate a second wire-pair that extends from the apparatus to a telephone line switching system, further characterized by switching means interconnecting electrical signals on the second wire-pair with the input port of the first modulator and interconnecting electrical signals at the output port of the first demodulator with the second wire-pair.

12. The carrier communication apparatus of claim 8 wherein said second modulator amplitude modulates a carrier signal in accordance with the magnitude of the digital data signal at its input, said carrier communication apparatus further including a second demodulator, having input and output ports, for amplitude demodulating electrical signals in the third frequency band received at its input port, whereby half duplex data communication service is provided.

13. The carrier communication apparatus of claim 12 wherein the digital data signal is binary and the carrier signal of the second modulator is switched off and on in accordance with the magnitude of the binary signal.

14. The carrier communication apparatus of claim 12 wherein the information content of the binary signal is contained in the time duration of each binary pulse.

15. A telephone line carrier system for communication at a user'"'"'s location comprising a master station and one or more remote stations, each station being parallel connected to a wire-pair that extents from the user'"'"'s location to a telephone line switching system, each station including a microphone, a loudspeaker and a hybrid circuit for interconnecting voiceband signals between the wire-pair and the microphone and loudspeaker,

CHARACTERIZED IN THAT

the master station further includes:

a first modulator, responsive to audio frequency signals at an output of the microphone for modulating said output signals into a first frequency band;

a demodulator, responsive to modulated signals on the wire-pair in a second frequency band, for converting same into audio frequency signals;

channel selecting means including one or more switch contacts on the master station for selecting a particular frequency band for interconnection between the wire-pair and the microphone and loudspeaker;

transmitter switching means having a pair of input ports for receiving audio frequency signals from the microphone and for receiving modulated signals from the first modulator, said transmitter switching means being responsive to the selecting means for switching signals to an output port thereof;

a second modulator, interconnected with the wire-pair, responsive to one or more master station control signals or status indicators, for encoding same into a digital data signal and for modulating the digital data signal into a third frequency band;

receiver switching means having a pair of input ports for receiving audio frequency signals from the wire-pair and for receiving demodulated signals from the demodulator, said receiver switching means being responsive to the channel selecting means for switching signals from an input port thereof to the loudspeaker, and

the remote station further includes;

a modulator, responsive to audio frequency signals at an output of the microphone for modulating said output signals into the second frequency band;

a first demodulator, responsive to modulated signals on the wire-pair in the first frequency band, for converting same into audio frequency signals;

channel selecting means comprising one or more switch contacts on the remote station for selecting a particular frequency band for interconnection between the wire-pair and the microphone and loudspeaker;

transmitter swtiching means having a pair of input ports for receiving audio frequency signals from the microphone and for receiving modulated signals from the modulator, said transmitter switching means being responsive to the selecting means for switching signals to an output port thereo;

a second demodulator, interconnected with the wire-pair, for demodulating said digital data signal in the third frequency band; and

receiver switching means having a pair of input ports for receiving audio frequency signals from the wire-pair and for receiving demodulated signals from the first demodulator, said receiver switching means being responsive to the channel selecting means for switching signals from an input port thereof to the loudspeaker.

16. A frequency-division multiplexed communication system for use at a telephone subscriber'"'"'s location comprising a master station and one or more remote stations, the master station being electrically connected to a central switching system with a wire-pair, each station including a microphone and loudspeaker for converting between audible sounds and electrical signals, a first modulator for frequency shifting voiceband electrical signals from the microphone into a first frequency band above 4 kHz, and a first demodulator for frequency shifting modulated signals in a second frequency band above 4 kHz into voiceband electrical signals for interconnection with the loudspeaker,

CHARACTERIZED IN THAT

each station is adapted to be electrically connected to the wire-pair in parallel, and each station further includes:

hybrid circuit means for interconnecting voiceband signals between the wire-pair and said microphone and loudspeaker;

means responsive to one or more station control signals or status indicators for encoding same into digital data signals;

a second modulator having input and output ports, responsive to the digital data signals at its input port for frequency shifting same into electrical signals in a third frequency band above 4 kHz at its output port;

means interconnecting the output port of the second modulator with the wire-pair;

a second demodulator, having input and output ports, for frequency shifting electrical signals in the third frequency band received at its input port; and

means interconnecting the input port of the second demodulator with the wire-pair.

17. A telephone line carrier system for installation at a subscriber'"'"'s location and interconnection with first and second telephone lines that extend from the subscriber'"'"'s location to a central switching location, the carrier system operating to distribute signals over the first elephone line, the carrier system including a master station and one or more remote stations bridged onto the first telephone line in a parallel electrical connection, each station including a hybrid circuit for interconnecting voiceband electrical signals between the first telephone line and a microphone and a loudspeaker,

CHARACTERIZED IN THAT

the master station termiantes the second telephone line and modulates voiceband signals therefrom onto the first telephone line for access by said one or more remote stations;

at the master station;

a modulator, having input and output ports, for converting voiceband electrical signals at its input port into electrical signals in a first frequency band above voiceband at its output port;

means interconnecting the input port of the modulator with the second telephone line;

means interconnecting the output port of the modulator with the first telephone line;

a demodulator, having input and output ports, for converting electrical signals at its input port in a second frequency band above voiceband into voiceband electrical signals at its output port;

means interconnecting the input port of the demodulator with the first telephone line; and

means interconnecting the output port of the demodulator with the second telephone line;

at the remote station;

a modulator, having input and output ports, for converting voiceband electrical signals at its input port into electrical signals in a second frequency band above voiceband its output port;

means interconnecting the input port of the modulator with the microphone, said microphone converrting audible sounds into voiceband electrical signals;

means interconnecting the output port of the modulator with the first telephone line;

a demodulator, having input and output ports, for converting electrical signals at its input port in the first frequency band above voiceband into voiceband electrical signals at its output port;

means interconnecting the input port of the demodulator with the first telephone line; and

means interconnecting the output port of the demodulator with a loudspeaker, said loudspeaker converting voiceband electrical signals into audible sounds.

18. Telephone station apparatus for use at a subscriber'"'"'s premises adapted to be parallel connected onto a first wire-pair and terminate a second wire-pair, said first and second wire-pairs extending between the subscriber'"'"'s premises and a telephone line switching system, the apparatus including means for transmitting and receiving electrical signals substantially in a frequency band below 4 kHz,

CHARACTERIZED BY:

a multiplexer, having an output port connected to the first wire-pair and a plurality of input ports, for converting electrical signals in the frequency band below 4 kHz at an input port thereof into electrical signals in a first frequency band above 4 kHz at its output port;

a demultiplexer, having an input port connected to the first wire-pair and having a plurality of output ports, for converting signals in a second frequency band above 4 kHz at its input port into electrical signals in the frequency band below 4 kHz at an output port thereof;

switching means interconnecting electrical signals on the second wirepair with one of the input ports of the multiplexer, and interconnecting electrical signals at one of the output ports of the demultiplexer with the second wire-pair; and

means interconnecting a digital data signal between a processor and another of the input ports of the multiplexer for converting same into an electrical signal in a third frequency band above 4 kHz at its output port, whereby a link between the first and second wire-pairs and a data channel for communication control over the first wire-pair is established.

19. Carrier communication apparatus adapted to be bridged onto a first wire-pair, the apparatus including microphone and loudspeaker transducers for converting audible sounds into voiceband electrical signals, a first modulator for converting the voiceband electrical signals from the microphone transducer into a first frequency band above 4 kHz, and a first demodulator for converting modulated signals in a second frequency band above 4 kHz into voiceband electrical signals for interconnection with the loudspeaker transducer;

CHARACTERIZED BY;

first hybrid circuit means interconnecting voiceband signals between the first wire-pair and said microphone and loudspeaker transducers;

second hybrid circuit means terminating a second wire-pair that extends from the apparatus to a telephone line switching system;

a second modulator having input and output ports for converting voiceband electrical signals into a third frequency band above 4 kHz, the output port being connected to the first wire-pair;

a second demodulator having input and output ports for converting modulated signals in a fourth frequency band above 4 kHz into voiceband electrical signals, the input port being connected to the first wire-pair;

means interconnecting signals received from the second wire-pair with the input port of the second modulator, and interconnecting signals to be transmitted over the second wire-pair with the output port of the second demodulator; and

a third demodulator having input and output ports, responsive to digital data signals at its input port for converting same into electrical signals in a fifth frequency band above 4 kHz at its output port, the output port of the third modulator being connected to the first wire-pair.