Abstract: When a group communication group call is initiated in a multi-site communication system, the communication processing information for that particular communication group call must be established. The communication processing information is formatted by a central controller which in turn transfers that information to a destination data base of a processing multiplexer switch. The information is then stored in the destination data base such that the particular communication group call may be quickly processed. When the communication unit that initiated the call ceases to transmit and another communication unit begins to transmit, the communication processing information is updated to reflect the change in the transmitting communication unit. This continues to happen until the particular communication group call has ended; once it has ended, the communication processing information is deleted from the destination data base.

Abstract: In a simulcast communication system (100), a communication unit (110-115) may request enhanced coverage area services by transmitting a request for enhanced signal quality to a central simulcast controller (101). Upon receipt, the central simulcast controller (101) identifies, based on information pertaining to the location of the communication unit, a set of transmitters (102-109) to enhance coverage in the area of the communication unit. The central simulcast controller determines enhanced coverage area delays for each of the transmitters and adjusts the respective delays of each transmitter such that transmitted signal quality is enhanced at the location of the communication unit.

Abstract: In a secure trunking communication system, limited secure service is provided during periods of limited service or failsoft operations using the following method. When the limited service or failsoft condition is detected, a limited secure service message or a failsoft service message, respectively, is transmitted to those system components utilizing encryption keys, including console interface units (CIU) (106-107) and communication units (111-113). Upon reception of the limited secure service message, the communication units load at least one limited service key. Simultaneously, the console interface units also load the at least one limited service key. Upon reception of the failsoft service message, the console interface units load at least one failsoft key. Simultaneously, the communication units also load the at least one failsoft key. The communication units and the CIUs use the limited service keys or the failsoft keys until normal operation is restored.

Abstract: A database unit monitors the communications occurring within at least one communication system for hardware identification codes of communication or broadcast units. Upon detecting the hardware identification code, the database unit compares the one received with a stored hardware identification code for the unit. When the stored hardware code does not match the one received, the database unit indicates that the unit has undergone an unauthorized modification.

Abstract: An analog-to-digital (A/D) circuit comprising a multi-pole gain stage, a quantizer, and a feedback stage is stabilized when an analog input signal is excessive in the following manner. A stabilization detector continually samples a representation of stabilization of the A/D circuit. When the representation of stabilization is unfavorable, the stabilization detector increases, via a stabilizer, phase margin by adjusting the pole locations of the multi-pole gain stage based on the degree of unfavorability of the representation of stabilization. With the increased phase margin, the A/D circuit continues to provide digital representations of the analog input signal.

Abstract: A voltage sensing circuit is used to determine when the current supply to a processing unit is under transition. During power up transitions, the voltage sensing circuit allows the processing unit to reset normally. During power down transitions, the voltage sensing circuit prevents the processing unit from resetting until a predetermined procedure has been completed, thereby assuring an orderly shutdown.

Abstract: In a communication system network that comprises a plurality of communication systems and a processing multiplexer, each of the plurality of communication systems is equipped with fallback operation circuitry. The fallback operation circuitry enables a communication system to operate as a standalone system when the interface buses that connect it to the processing multiplexer fail. In addition, the fallback operation circuitry enables the communication system to be reconnected to the processing multiplexer when the interface buses resume proper operation.