Portable radio telephone

• US 4,430,755 A
• Filed: 05/14/1981
• Issued: 02/07/1984
• Est. Priority Date: 05/14/1981
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: James, Gordon W., Kuznicki, William J., Nadir, Mark, Nieds, Jerome A.
• Primary Examiner(s): Rubinson, G. Z.
• Assistant Examiner(s): Brady, W. J.
• Application Number:
  US06/263,797
• Time in Patent Office: 999 Days
• Field of Search: 179/2 E, 179/2 EA, 179/2 EB, 179/2 EC, 455/31, 455/38, 455/54, 455/56, 455/76-79, 455/82, 455/83, 455/32, 455/35-37, 455/161, 455/166
• US Class Current: 455/77
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

A system for radio-telephone communication between a user at a remote location and the commercial telephone system or between two users at remote locations comprises a fixed terminal that is connected by wire lines or the like to the commercial telephone system and a plurality of portable radio units. The terminal is equipped for duplex operation on a plurality of channels, each of which uses separate frequency bands for transmitting and receiving. Each of the portable units is a simplex transceiver adapted to receive on each of the frequencies of transmission from the terminal and to broadcast on each of the frequencies received by the terminal. The terminal places a channel acquisition tone on an unused channel that is the next to be used. The terminal calls portable unit by shifting channel acquisition tone to another channel and broadcasting an identifier to the portable unit. The called portable unit responds to its individual identifier by sounding an audible alert and producing an audible verbal message if one is sent from the terminal. A portable can also originate a message by calling the terminal. A delay period provides time for the portable to recognize its identifier before beginning to scan for channel acquisition tone. Circuits and logic in the portable produce a busy signal if the user attempts to call at a time when the portable is not receiving channel acquisition tone. A reset in the portable unit provides means for the user to terminate the call.

Claims

1. In a simplex portable transceiver tuned to a first channel of a plurality of channels that may contain a channel acquisition tone that is converted to an electrical signal with audio variations and applied to a limiter to produce limited audio, an automatic scanner controlling a change to a second of the plurality of channels, the scanner comprising:

an active filter (272) connected to the limiter, the filter (272) passing a narrow band of frequencies including the frequency of the channel acquisition tone;

a peak detector (274) connected to the active filter (272) and responsive to the limited filtered channel acquisition tone to produce negative-going pulses;

a NOR gate (276) connected to the peak detector (274) to produce an output;

a J-K flip-flop (278) connected to NOR gate (276) and set by the output from NOR gate (276) to produce an output in the absence of channel acquisition tone;

a programmable counter (282) set to the output of J-K flip-flop (278) to produce a system clock signal on a line (284) and an output square wave having a period of a shorter time when channel acquisition tone is received and a longer time when channel acquisition tone is not received;

a four-bit counter (280) connected to J-K flip-flop (278), programmable counter 282 and NOR gate (276), counter (280) being clocked by the output square wave of programmable counter (282) and reset continually by the output from NOR gate (276) that indicates that channel acquisition tone is present; and

a NOR gate (286) connected to programmable counter (282) to produce an output that prevents scan when the receiver is receiving channel acquisition tone or during a scan delay or use of the transceiver.

2. In a simplex transceiver tuned to a first channel of a plurality of channels that may contain a channel acquisition tone, an automatic scanner controlling a change to a second of the plurality of channels, the scanner comprising:

an active filter coupled to a limiter for selecting a channel acquisition tone;

a peak detector coupled to said active filter and responsive to said channel acquisition tone to produce negative going pulses;

a NOR gate coupled to said peak detector;

a flip-flop coupled to said NOR gate to produce an output in the absence of channel acquisition tone;

a programmable counter set by the output of said flip-flop to produce a system clock signal and having an output square wave with a period of a relatively shorter time when channel acquisition tone is received and a relatively longer time when channel acquisition tone is not received;

a counter connected to said flip-flop, programmable counter and said NOR gate, counter clocked by the output square wave of programmable counter and reset continually by the output from said first NOR gate that indicates that channel acquisition tone is present; and

a second NOR gate coupled to said programmable counter to produce an output that prevents scan when the receiver is receiving channel acquisition tone or during a scan delay or use of the transceiver.

3. In a simplex portable transceiver tuned to a first channel of a plurality of channels that may contain a channel acquisition tone that is converted to an electrical signal with audio variations and applied to a limiter to produce limited audio, an automatic scanner controlling a change to a second of the plurality of channels, the scanner comprising:

an active filter coupled to a limiter for selecting a channel acquisition tone;

a peak detector coupled to said active filter and responsive to said channel acquisition tone to produce negative going pulses in the presence of channel acquisition tone;

a first gate coupled to said peak detector;

a flip-flop coupled to said first gate to produce an output in the absence of channel acquisition tone;

a programmable counter set by the output of said flip-flop to produce a system clock signal with a relatively short period when channel acquisition tone is received and a relatively longer period when channel acquisition tone is not received;

a counter coupled to said flip-flop, said programmable counter and said first gate, said counter clocked by the output of said programmable counter and reset continually by the output of said first gate when channel acquisition tone is present; and

a second gate with a first input coupled to said programmable counter and a second input coupled to said counter to prevent scan when the receiver is receiving channel acquisition tone or during a scan delay or use of the transceiver.