Abstract: A communication system (100) that varies the channel usage requirements of its communication resource assignment grant signals to accommodate the varying needs of communication units themselves as well as accommodating current loading conditions on an assignment resource.

Abstract: Improved Q factor for stripline and microstrip filters can be realized by increasing the thickness of conductive paths. Increased conductive paths in a stripline and microstrip filter can be realized by forming slots (20) in a block of dielectric material (12) which permit an increased thickness of transmission path thereby improving the Q factor of the material by reducing at least resistive losses.

Abstract: A simulcast transmission system (150) is disclosed in which a primary (402), a first, and a second transmitter site (302) form a first communication loop (403). The first communication loop (403) has at least a first and a second audio path, each of which are associated with a path identification (ID). The first and the second path IDs are also associated with a set of transmission delay parameters which are stored (401) at both the first and the second transmitter sites. The primary transmitter site (402) detects a location of an inoperative communication link (409) within the first audio path, and switches from the first audio path to the second audio path, whereby the second audio path does not traverse the inoperative communication link. The primary transmitter site (402) then broadcasts (512) a path condition ID to the first and the second transmitter sites. The first and second transmitter sites then retrieve (514) the set of transmission delay parameters associated with the second audio path.

Abstract: A broad-band microwave waveguide radio frequency splitter and combiner (70 and 100) can be realized by using TEM mode wave propagation to edge guide mode wave propagation conversion performed by magnetically biased material (16) and directionally opposed magnetic fields (20 and 22) and a waveguide such as a microstrip (10) or a stripline (50) to spatially separate a TEM mode signal into two or more components.

Abstract: A radio communication controller (106, 401) is disclosed which is capable of accessing a database having a subscriber unit identification code (302, 601) and a preselected calling code, or area code, accumulating a keyed Public Switched Telephone Network (PSTN) telephone number from the subscriber unit wishing to make an interconnect call (110, 407), and comparing (215, 518) this area code with that of the controller site. The controller, as employed by the invention, is further capable of deciding whether or not the area code is required for completing the interconnect call, and if so, prefacing (217, 520) the accumulated PSTN telephone number with the area code preselected by the user of that subscriber unit.

Abstract: A modem, or data communications device, that is testable independently of a DTE device permits remote testing of it automatically by a network management computer or controller reducing required operator intervention. A data communications network that has possibly hundreds of these modems requires substantially less operator intervention.

Abstract: A ceramic filter (10) can be surface mounted. Input/output pads (18 and 20) through which electrical signals pass are located on one surface of a block of dielectric material (12) to permit use of the so-called surface mount manufacturing techniques. No wired connections to the ceramic bandpass filter block are required.

Abstract: An asynchronously resettable counter/divider (25) in a phase-locked loop (PLL) for a frequency synthesizer (12) reduces the lock-up time for the PLL by resetting the resettable counter/divider when the phase difference between the output signal from a VCO (20, 21) and a low frequency reference signal (30) exceeds a predetermined value.

Abstract: An improved method and apparatus for demodulators for MSK signals. Demodulation of the MSK signals is performed at base-band other than at IF frequencies. A digital signal processor is preferably used.

Abstract: A transmission line using superconductors instead of conventional conductors substantially reduces ohmic losses compared to conventional conductors. The superconductors are cooled by refrigerant flowing through a hollow superconducting inner conductor. The refrigerant is transported to the inner conductor using a novel connector.

Abstract: A method of configuring directional antennas to more fully radiate a geographic region serviced by a simulcast radio system can reduce the number of omni-directional antennas used by prior art methods. Directional antennas having significant differences between frontal and rearward radiated signal levels are used to provide large signal amplitude differences when signal phase differences in the simulcast coverage area become appreciable.

Abstract: A typical multi-site trunked communication system comprises communication units that are arranged into talk groups, communication resources distributed among communication sites, and a communication resource allocator. In such a system, a methodology is incorporated that allows communication units to override communication site busy conditions, where the communication site busy conditions prohibits placement of group calls until all communication sites have an available communication resource. The communication site busy condition may be overridden by a communication unit by initiating a busy override signal. Once the busy override signal is initiated, the communication resource allocator allocates, in each site, a communication resource to the communication group of the requesting communication unit.

Abstract: This key management system effectively solves the key distribution problems of distance, time, operator error, and security risk by transferring encryption keys with appropriate system information between a key management controller (101) and a remote keyloader (109). The keyloader (109) is then coupled to a communication device to transfer (327) the keys and receive (329) identification information from the communication device. The keyloader (109) then sends (323) the information to the key management controller (101) that controls the distribution of the encryption keys and collection of the communication device identifications.

Abstract: The present invention discloses a communication system network that comprises a plurality of communication systems and a processing multiplexer. The communication systems, which may be either conventional communication systems and/or trunked communication systems, transmit digitized audio signals and communication system data to the processing multiplexer. Based on signal destination data, which is part of the communication system data, the processing multiplexer processes the digitized signals and routes the resultant signals to the appropriate signal destinations of the communication systems.

Abstract: A communication unit having a dynamic control resource scan list utilizes the scan list to more effectively roam from the current trunked communication system to other trunked communication systems. The scan list contains control resource information of trunked communication systems, where the control resource information is the control resources of the system and the features offered by that system.

Abstract: A self checking electronically erasable programmable array logic (EEPAL) that comprises an input receiver, a programmable array, an error detection code storage array, an error detection circuitry, and error signalling circuitry is disclosed. The self checking EEPAL verifies the storage integrity of each cell within the programmable array during the programming of the EEPAL, after completion of programming the EEPAL, and prior to executing the algorithm stored in the EEPAL.

Abstract: An inductor structure, that houses a shorted transmission line inductor, includes components mounted within the volume carrying the shorted transmission line. Dielectric substrate layers which carry the shorted transmission line components and the electronic devices when sandwiched together can be coated with a metallic layer that acts as a shield protecting the internal components from external undesired sources. Mounting components within the inductor volume potentially saves space on a circuit board.

Abstract: A method and arrangement for providing damping of undesired modes of piezoelectric vibrators is disclosed that eliminates the tedious and often inaccurate methods of known mass-loading techniques. Instead, the arrangement relies on physically altering a controlled amount of the piezoelectric material located at a predetermined point to effect the selective damping needed to minimize the undesired responses and to minimally interfere with the desired mode of operation.

Abstract: In a communication system wherein subscriber units and dispatch consoles are equipped with a display device and an image storage device. By having the communication unit so equipped, the operator of a communication unit can readily identify an operator of a transmitting communication unit by displaying an image of the transmitting communication unit throughout the call.