Abstract: An apparatus and method of reducing a peak envelope power of a linear power amplifier (10) amplifying a plurality of channels is provided. The method includes the steps of measuring (104) the peak envelope power of the linear power amplifier, measuring a channel activity level (101) of each channel of the plurality of channels, and, when the peak envelope power exceeds a first threshold, changing (103, 106) at least one parameter of a channel of the plurality of channels having a channel activity level exceeding a second threshold to reduce the peak envelope power.

Abstract: The dual mode communication network comprises a first communication system having a frame structure and a first traffic channel protocol and a second communication system having the frame structure and a second traffic channel protocol. In the network, only one of the first and second traffic channel protocols supports forward error correction coding.

Abstract: A digital radiotelephone system employs vocoders to convert between analog speech and a digital format suitable for transmission via radio. Under most circumstances, the highest data rate is selected for optimum audio quality. When the system occupancy exceeds a particular threshold, as detected at the fixed site of the system, some or all of the vocoders are instructed to switch to a lower data rate to provide for an increase in the number of communication channels. Further, a portable subscriber unit may autonomously change its vocoder data rate depending upon the charge state of its battery.

Abstract: The apparatus first measures the peak power of a multichannel signal, or representation thereof. The peak power is compared with one or more peak power threshold values. If the measured peak power exceeds a threshold value, the multichannel signal is attenuated prior to being processed by the linear power amplifier.

Abstract: A communication unit (10) transmits a first signal (12) that has a plurality of holes (44) therein during the occurrence of which another communication unit may interrupt. A repeater (14) receives the first signal and transmits a second signal (16) comprising the information in the first signal, and a plurality of digital coded squelch words synchronized with the holes to indicate the location of at least one of the holes in the first signal (i.e., the time at which at least one of the holes will occur). In one embodiment, each hole occurs after each pair of coded squelch words, and accordingly the pairs of coded squelch words are marked to indicate the times of occurrence of holes in the first signal.

Abstract: A method for interrupting a radio transmission in a quasi-duplex radio-frequency communication system. The method of the present invention includes the step of transmitting a signal (22), with periodically-occuring holes (24) therein, by a first communicatioin unit (10) to at least a second communication unit (12). The transmitted signal (12) includes an audio information portion (16) and information packets (23). Each information packet (23) specifies the time of occurence of the next hole (24). The second communication unit (12) initiates an interruption of the transmission made by the first communication unit (10) by transmitting an interrupt request signal (31) to the first communication unit (10) at a time specified by an information packet (23) received by the second communication unit (12). When the first communication unit (10) receives the interrupt request signal (31), it processes the interrupt request signal (23) to determine whether it complies with predetermined criteria.

Abstract: A communication system that provides pseudo-duplex communications between communication units. A control slot is used to allow a receiving unit to transmit a request to interrupt, and to instruct a transmitting unit to interrupt its transmissions and to begin receiving.

Abstract: In a communication system where outbound communications are comprised of a TDM format, and inbound communications are not, and wherein the outbound communications occasionally include system control information, a method for allowing a transmitting unit to occasionally interrupt its transmissions to allow reception of system control information.

Abstract: A trunked radio subscriber requesting dispatch service transmits a request for a channel and immediately begins to speak without waiting to receive permission to access the channel. The subscriber radio locally records the information to be transmitted and, upon being assigned a channel, begins to reproduce and transmit the information. Recording and reproduction provides delay to span the time between request for and assignment to a channel and eliminates the need for the subscriber to wait to transmit or to quickly seize a channel assigned after an initial refusal. This enhances overall response time and increases time available for transmitting information signals. During interconnect calling, a trunked system alternately assigns inbound and outbound frequencies only as required for back-and-forth communication between simplex radio and duplex wireline subscribers. Voice buffering allows the parties to begin talking during the delay between request for and assignment of frequencies.

Abstract: An adaptive audio filter system is disclosed which comprises a filter means capable of producing a plurality of frequency response characteristics. A control signal generating means provides a control signal to the filter means to enable a particular frequency response. The control signal is based upon the signal to noise ratio.

Abstract: A time division multiplexed (TDM) communication system is disclosed, which apportions radio frequency communication channels into at least two time slots. Voice signals for transmission on this system are analyzed and vo-coded into a digital signal that is transmitted during one or more of the time slots. Received messages are recovered from at least one of these time slots and the voice message synthesized from the vo-coded signal. In this manner multiple voice messages may be transceived in a time division multiplexed manner on a single narrowband communication channel.

Abstract: A general purpose data control and information system particularly well adapted for multiple unit radio communications providing reliable enhancement to normal voice systems. The system provides addressing capability along with data transfer and utilizes handshake and retransmission protocol to enhance flexibility and reliability. The system utilizes fixed length signalling packets, with error correction encoding, to permit data transfer, transmitter identification and control and status monitoring.

Abstract: A communications system central controller which regulates the access of a plurality of remote units to a single communications channel is disclosed. The central controller establishes a period of time wherein a remote unit may request service following the transmission of another remote unit. The central controller interprets the remote unit request for service, stores the request, and grants permission for the remote unit to transmit its message in accordance with the priority in the storage means. The grant of service is revoked by the central controller after a predetermined period of time following the conclusion of the remote unit transmission.

Abstract: A remote unit which transmits and receives messages within a fleet of remote units on a single communications channel shared by a plurality of remote unit fleets is disclosed. Access to the channel is regulated by a central control station which transmits control signals on the channel. To obtain service, a remote unit transmits a request synchronized by one of the control signals. Upon receiving a grant of service from the central control station, the remote unit may transmit a message to its fleet. At the conclusion of the message, an end-of-transmission condition is indicated by the remote unit.

Abstract: A battery saving system for a portable duplex communications system such as a portable telephone system includes a voice operated transmitter within each portable unit which automatically transmits radio signals upon application of audio signals thereto and discontinues transmission upon termination of the audio signals to conserve battery power. A companion receiver includes a fast acting squelch system to substantially eliminate the noise bursts occurring between transmissions by said portable unit.

Abstract: A communication system of the type wherein a central station assigns a limited number of information channels to a requesting one of a plurality of remote stations is disclosed. The requesting station sends its identification signal along with the request signal to the central station on a signal channel. The central station classifies the requesting station in either a priority or a non-priority queue. The priority queue corresponds to those stations which are continuing an on-going interchange, whereas the nonpriority queue contains those stations which wish to initiate an interchange. Stations are prioritized in the queues on a first-in/first-out basis.The central station constantly monitors the information channels and, as channels become available, assigns the channels first to stations in the priority queue, then to nonpriority queue stations.