Abstract: When a portable radio (110) receives a transmission from a mobile radio (105), the portable radio (110) mutes a speaker volume of the portable radio (110) for a duration of the transmission from the mobile radio (105). In an arrangement of the mobile radio (105) and the portable radio (110) where both radios transmit and receive on a same communication resource channel and both radios are in close proximity, acoustic feedback may be avoided.

Abstract: Adjustment of the output frequency of a frequency synthesizer can be optimized in the following manner. Once a frequency adjustment request is detected, which indicates a selected frequency, a frequency difference is calculated between the selected frequency and the present frequency. A frequency scaling factor is then determined. Once the frequency difference and the frequency scaling factor are determined, a frequency adjustment time is calculated based on a proportional relationship between the frequency difference and the frequency scaling factor. The bandwidth of a multi-bandwidth filter is adjusted to a second bandwidth for the duration of the calculated frequency adjustment time. The output frequency of the frequency synthesizer is adjusted from the present frequency to the selected frequency prior to the expiration of the frequency adjustment time. Upon expiration of the frequency adjustment time, the bandwidth of the multi-bandwidth filter is adjusted from the second bandwidth to the first bandwidth.

Abstract: In a wide area communication system that includes a central controller, a plurality of sites, and a plurality of subscriber units, a requesting subscriber unit can locate a neighboring subscriber unit in the following manner. Each of the plurality of subscriber units registers with the central controller. The central controller stores registration information in a database. When the requesting subscriber unit transmits a request for a subscriber identification of a neighboring subscriber unit, the central controller determines whether the neighboring subscriber unit exists. When the neighboring subscriber unit exists, the central controller transmits the subscriber identification of the neighboring subscriber unit to the requesting subscriber unit.

Abstract: Binary encoded data may be detected in a stream of data, by first detecting data transitions. From the detected data transitions, a first pulse is generated when successive data transitions are detected within a predetermined period of time and a second pulse is generated when successive data transitions are not detected within the predetermined period of time. The first and second pulses have the same duration but the amplitude of the first pulses is half of the amplitude of the second pulses. The first and second pulses are filtered by a bandpass filter and compared with a predetermined threshold. When the filtered pulses are above the predetermined threshold, the received stream of data is binary encoded data. When the filtered pulses are below the predetermined threshold, the received stream of data is not binary encoded data.

Abstract: Determining transmit time of a received signal in a simulcast multi-site communication system begins when a communication unit transmits a message to one or more network receivers. Each receiver transports the received signal with a time stamp to each transceiver in the network via a digital communication network. Each transceiver calculates a wait period, during which, the transceiver may receive the signal and time stamp message from another receiver. Once the wait period expires, each transceiver, using a substantially similar selection method, selects the same received signal to broadcast. Each transceiver then determines a launch time for transmission of the selected received signal, wherein the launch time accommodates the worst case expected transport delay through the digital network.

Abstract: Processing of dispatch calls in a simulcast multi-site communication system begins when a source communication unit transmits a message to one or more network receivers. The received signals are analyzed immediately at the received sites for signal quality. Each of the signals are time stamped to identify when they where received. The received signals are transported with their time stamp and signal quality metric to each of the other sites via a digital communication network connecting the sites. A master transmitter site determines the receiver source with the best quality signal as indicated by the signal quality metric. The master transmitter then transports the chosen best quality signal to each of the other sites via a digital communication network. Each transmitter site performs a transmit operation by storing the chosen best quality signal until it is time to transmit the signal in phase with all the other transmitter sites in a simulcast manner.

Abstract: Power amplifiers, which include a feedback element, may be protected from excessive operating power levels by adjusting the feedback element to reduce the drive signals to the power elements. This is accomplished by sensing the output power of the power amplifier to produce a sensing signal. When the sensing signal exceeds a predetermined threshold, a feedback element is adjusted to produce an increased feedback signal. The increased feedback signal is subtracted from an input signal, thus decreasing the drive signal. With the drive signal reduced, the output power is reduced proportional to the adjustment of the feedback element.

Abstract: In a secure trunked communication system that includes a central controller, communication between a distribution panel and a limited number of console interface units may be achieved in the following manner. At power up or upon a reset condition, the distribution panel transmits a status check message to each console interface unit in the system. Console interface units that are active respond by transmitting an acknowledgement. Upon receiving the acknowledgement, the distribution panel transmits the addresses of the active console interface units to the central controller. When the distribution panel receives secure information from the central controller, it interprets the information to identify a target console interface unit and transmits the received secure information to the target console interface unit.

Abstract: Audio communication may be established between a plurality of communication units in a communication system that includes a dispatch switching center in the following manner. A first communication unit generates information to be distributed to a second communication unit. The dispatch switching center receives a digital packet including the information to be distributed, and ascertains an identifier associated with the second communication unit. The dispatch switching center replicates the information to be distributed, and uses the identifier to distribute the replicated information to the second communication unit.