Abstract: An alarm system for sensing an alarm condition within a relevant alarm area includes one or more portable alarm units for sensing an alarm condition. Each alarm unit includes a radio frequency transmitter for identifying the alarm unit and a secondary, audio, transmitter for defining the relevant alarm area. The system also includes a plurality of transponders. Each transponder includes a primary receiver for receiving a radio message from an alarm unit and a secondary receiver for receiving an audio signal from the alarm unit. A real-time clock in each transponder provides the elapsed time between receipt of a primary and receipt of the secondary alarm signals. The alerted transponders then transmit to a control unit a transponder address code, an alarm unit identification code and an elapsed time indicia. Based on the address code or codes and the minimal elapsed times detected by the control unit, the relevant alarm area can be determined.

Abstract: Method and apparatus are provided for bi-directional audio and data communications enabling a time-division multiplex control center system and distributed system intelligence enabling efficiency and reliability.

Abstract: An inductorless quadrature demodulator for frequency modulated signals is disclosed. A limited FM signal is passed through an active filter (26) and a phase shift network (30) to produce a quadrature signal. The limited FM signal is compared with the quadrature signal in an EXCLUSIVE OR gate (24) and then low pass filtered (36) to obtain recovered audio. The active filter (26) includes a transconductance amplifier (60) whose center frequency can be adjusted by appropriate adjustment of the amplifier's bias current. The bias current is temperature compensated to allow operation of the demodulator over a wide temperature range.

Abstract: The communications system may include wireless two-way communications equipment having selectable functions and various operational features. Control modules each include mechanisms for providing indicia representative of the status of the features of the communications equipment and mechanisms for generating data for controlling the functions to be selected on the communications equipment. A group of the control modules are coupled to a panel module which selectively communicates with each of the control modules in the group. An interface circuit is coupled to a plurality of the panel modules for selectively communicating with each; the interface circuit includes a microprocessor for writing indicia data to each of the selected control modules via the selected panel module and reads the control data generated by the control modules. The periodic scanning and reading of information is utilized to ascertain changes in the data.

Abstract: A method and means for reducing noise in a GaAs FET oscillator circuit is described. The circuit of the present invention achieves low noise oscillator operation by driving the gate input of the GaAs FET oscillator circuit with a source of voltage which exhibits a low impedance at baseband frequencies and driving the drain input with a source of current which exhibits a high impedance at said frequencies. The present invention further operates to control the D.C. voltage present on the drain terminal of the GaAs FET device regardless of the drain current, while simultaneously maintaining a constant D.C. drain current at some predetermined value which corresponds to optimum low-noise operation.

Abstract: An embodiment of the invention includes a binary linear phase response filter having a plurality of weighted outputs and a summing circuit which sums groups of the weighted outputs. A polarity inverting mechanism is provided for selectively changing the polarity of the summed outputs from the summing circuit means. An encoding circuit controls the polarity selection in accordance with the logic rule for converting non-return to zero (NRZ) data into return to zero data. Another summing circuit sums the outputs of the polarity inverting mechanism and provides a filtered multilevel data output.

Abstract: A improved microwave dielectric oscillator module which is provided with a removable temperature compensated dielectric resonator channel element is described. The removable temperature compensated dielectric resonator channel element cooperates with an electrically shielded housing. A substrate is mounted within the housing. Microstrip or stripline conductive patterns deposited on the substrate couple energy from the removable dielectric resonator to the remainder of the oscillator circuitry. The oscillator achieves wideband operation utilizing a GaAs FET transistor as the oscillators active element in conjunction with an intergral trombone-line phase adjuster.

Abstract: A digital lock detector for a phase-locked loop accumulates out-of-lock pulses which are derived from a high frequency clock signal. The out-of-lock pulses are gated by an out-of-phase indicator signal and a pulse centered around the phase-locked loop output cycles to reduce the effect of relative phase jitter between the input and output signals of the phase-locked loop. The digital lock detector utilizes two counters in series which are reset independently to provide resistance to fading signal conditions. In addition, the lock detector circuit requires several consecutive long out-of-lock indications before an out-of-lock condition is indicated.

Abstract: A method and means for controlling telephone interconnect traffic on a trunked radio system is described. The present invention continuously monitors all types of communication traffic on the system and in response to an increasing dispatch access delay, reserves certain repeaters for dispatch use only during a predetermined period. The present invention also contemplates a system in which the number of simultaneous telephone interconnect calls permitted on the system during a predetermined period is dynamically altered in response to system loading. In addition, the present invention establishes a variable, periodically updated, maximum interconnect call length based on the current system dispatch access delay.

Abstract: An improved ceramic stripline filter assembly is disclosed which provides optimized performance characteristics by careful control of the gap thickness between the filter halves during the assembly process. The filter arrangement utilizes paddle leads which include central cavities or pocket holes to accept any excess solder during filter assemblage. Close tolerances are thereby obtained regarding the referenced gap thicknesses from filter to filter.The method of fabricating the stripline filter assembly contemplates the use of a leadframe with the leads extending laterally from a unitary support structure. The leads are then cut or otherwise separated from this integral support after attachment of the leads to the filter body connection points. They may be pre-formed to any predetermined pattern after such separation.

Abstract: An improved simulcast transmission in which a signal transmitted by a master station provides a reference frequency signal, as well as a voice and data path, is described. The system can be configured such that a master station can transmit AFSK data and voice or FSK data and voice. In either case, the remote transmitter will retransmit FSK and voice.

Abstract: Disclosed, herein, is an Automatic Gain Control (AGC) signal processor and a method for generating an AGC signal in a phase-locked receiver. An incoming signal, exhibiting both coherent and incoherent characteristics, is filtered to obtain the desired bandwidth. The filtered signals are amplified to maintain an amplitude relationship between the coherent and incoherent signals. The incoherent signals are conditioned in the same circuit, but in a different manner, than coherent signals are conditioned. The conditioned signals are utilized to generate an AGC signal such that an AGC signal is generated in a single circuit for both coherent and incoherent signals, although by differing circuit responses, depending upon the conditioning of the incoming signal.The preferred embodiment of the novel AGC processing contemplates a full wave rectifier as its signal conditioner. Another embodiment contemplates negative peak detection as its conditioner.

Abstract: A receiver for receiving and demodulating FSK modulated data signals has improved sensitivity over substantial frequency offsets between the transmitter and receiver local oscillator, and low spurious electromagnetic radiation. A quadrature coupler splits the received signal into in-phase and quadrature phase signals which are then mixed down to baseband, filtered, and limited. An RC circuit at the output of a four flip flop demodulator averages the flip flop output signals. A voltage comparator outputs a logical 1 if the voltage at the output of the RC averaging circuit is greater than one-half the supply voltage; otherwise the comparator outputs a logical zero.

Abstract: A portable audio-visual demonstration apparatus which provides operational instruction and functional simulation or particularized electronic equipment for training and exhibition purposes is disclosed. The preferred embodiment of the invention is the application of the demonstration apparatus to communications equipment, specifically FM two-way mobile radios. This embodiment comprises: a plurality of actual radio control heads wherein all radio controls and functions are simulated to be fully operational; a display panel with overlying translucent forms which is illuminated to display the corresponding radio operational response; a tape deck which plays a cassette wherein voice instruction has been pre-recorded; and a portable hand-carried suitcase package which incorporates the above elements with its own power supply.

Abstract: In a circuit arrangement for providing a current having a controllable temperature coefficient of current, a diffused resistor (334) is used to set up a reference current in a current source (40) which has a temperature coefficient dependent upon the diffused resistor. A current mirror (352, 354, 356) receives the reference current and passes a portion of it through an ion implanted resistor (360). The output current has a temperature coefficient which is a function of the original temperature coefficient of current and a nonzero algebraic multiple of the temperature coefficient of the implanted resistor. By appropriate selection of the resistor values and types, the temperature coefficient of the output current can be set to any desired value.

Abstract: Method and apparatus are provided for control of a dedicated data slot in a time-division multiplex system for both voice and data communications enabling equal access to the data slot, efficient data throughput and reliability.