Abstract: The invention is a decoder for decoding serially received signals. The decoder includes circuitry for calculating the period of each signal in a group of the serially received signals. The decoder averages the periods of the group and calculates the groups average variance. Additional circuitry in the decoder calculates an average variance threshold. Detection circuitry within the decoder takes the average period, the average variance and the average variance threshold of the group of signals and produces a detection signal when the average period remains constant and the average variance remains below the average variance threshold for a predetermined minimum time period.

Abstract: An active filter includes a first active stage including an operational amplifier and feedback means wherein the non-inverting input terminal of the operational amplifier is at a ground potential; a second active stage configured in the form of Miller integrator using an operational amplifier and connected in series with the first active stage; and means connecting the non-inverting terminal of the operational amplifier of the second active stage to the inverting terminal of the operational amplifier of the first active stage for enhancing the filter characteristics.

Abstract: A low-profile crystal package wherein the wire bonding operation from the electrode pattern of the crystal plate to the terminal posts may be accomplished without fear of fracture of the crystal plate itself. The crystal blank is positioned on a support member which in turn initially sits on a ring of indium. In this position, the crystal blank is not in contact with the split center support post whose top surface is covered with indium paste, and is supported around its periphery during wire bonding. When all the wire bonding operations are effectuated, the assembly is subjected to sufficient heat wherein the indium material will melt, which will cause the support member to be drawn downward, thereby resulting in the crystal plate being supported and fastened only by the center supports, with the periphery of the crystal plate being free to vibrate with no extraneous dampened support.

Abstract: A unique bit data operated squelch for use with a demodulator detector for phase shift keyed digital signals. The squelch detects transitions by testing a register of baseband demodulated sample synchronized to the data bit edges. The inventive data operated squelch provides bit detection with programmable parameters and is particularly suitable for implementation utilizing a microprocessor.

Abstract: A method utilizing a localized electrical field to precisely determine the surface contour of a substantially flat wafer of piezoelectric material having a slight convexity in its opposing faces.

Abstract: Voice signals subjected to differential modulation such as CVSD modulation are made more intelligible by differentiating an electrical analog of the voice signal, clipping peaks of the differentiated signal, integrating the clipped differentiated signal, and applying the integrated signal to a differential modulator such as a CVSD modulator.

Abstract: A supervisory control system for interrogating a large number of remote units. A pseudorandom sequence of bits are generated by central control in cycles and received by the remote units. Each remote unit is provided with a pseudorandom bit sequence generator. Upon coincidence of the pseudorandom bit sequence from the central control and the remote unit and upon detection of the address of remote unit and of the specific point in that remote unit, the remote unit sends back to the central control the status information of the selected point during the next succeeding bit time interval. In this manner the statuses of entire set of remote units are interrogated and reported. In accordance with a further aspect of the present control system, the control system commands the remote units for action and the remote units send back command acknowledge signals.

Abstract: An antenna is provided which exhibits a relatively small size and is capable of resonating at two different frequencies. The antenna includes two helically wound elements which resonate at a first resonant frequency. A conductive member extends through and beyond one of the two helical elements to cause the antenna to resonate at a second resonant frequency.

Abstract: A variable impedance synthesis circuit is provided for generating a selected impedance, whether real or complex, at a predetermined port. The variable impedance synthesis circuit exhibits the selected impedance in response to control signals applied thereto.

Abstract: A frequency synthesized transceiver capable of tuning to a plurality of communication channels is disclosed. The transceiver includes a receiver section and a transmitter section which are coupled to the synthesizer which generates the appropriate injection signals to achieve tuning. The frequency synthesizer includes a multiposition switch which accesses various addressable memory locations in a programmable read-only memory where the appropriate divisors are stored to cause tuning of the synthesizer to the appropriate communication channel. The multiposition switch has a minimum number of interconnection lines connected to an analysis circuit which identifies the switch position. A zone selector switch enables grouping and easy retrievability of channels. The divisors are supplied to a single synchronous binary swallow counter which works in conjunction with a dual modulus prescaler to monitor the frequency output of the voltage controlled oscillator.

Abstract: A receiver of digitally encoded voice signals that may be encrypted according to a plurality of keep subjects a received signal to decryption according to each of the keys. Decrypted signals are tested for the presence of modulation, and the signal, if any, that is decrypted is recovered for use. If it is desired, a visual indication may tell a user which key is being used to decrypt the signal.

Abstract: A rotatable control with an integral switch comprises conductive inner and outer shaft in a concentric configuration. The inner and outer shaft are electrically insulated from one another and frictionally coupled to allow concentric simultaneous rotation. The assembly is covered with a flexible insulating shroud which has a switch contact located on the upper interior surface thereof. Conductive spring members are clipped around the lower portion of the inner and outer shaft to allow electrical connection to a circuit board.

Abstract: A high efficiency radio frequency amplifier is provided which includes stabilization circuitry which is selectively actuated during periods of time when undesired amplifier circuit operating conditions are present which tend to cause amplifier oscillation. Otherwise, the stabilization circuit remains in effect decoupled from the amplifier so as not to unnecessarily draw power from the amplifier circuit when its action is not required to prevent undesired oscillation of the amplifier.

Abstract: A pager includes means for receiving emergency calls immediately upon reception of the emergency calls and means for receiving non-emergency calls and, storing the non-emergency calls for subsequent readout upon interrogation. The pager is shown implemented in hard-wired logic form and alternatively in a programmable microprocessor form.

Abstract: A whip antenna assembly of conductive cable, conductive base section, conductive protection knob and a environmental cover. The conductive antenna cable is constructed of multiple layers of brass plated stainless steel wire wound in a helix about a single wire strand which serves as a central core. The conductive base section and conductive protection knob consist of a zinc alloy and are injection cast onto opposite ends of the conductive antenna cable. An environmental cover made from polyurethane is injection molded over the subassembly of conductive antenna cable, conductive base section and conductive protection knob.

Abstract: A method for synchronizing the scrambling sequences of communicating scrambler units of a privacy communications system in a reliable and secure manner. The method is particularly adapted for use in noisy or fade prone transmission environments, and permits late entry of authorized third parties to the system. The method utilizes digital sequences interleaved periodically with scrambled analog information to provide reliable synchronization.

Abstract: A unique ceramic bandpass filter is disclosed that is comprised of a dielectric block having one or more holes extending from its top surface to its bottom surface and further having input and output electrodes each disposed on the dielectric block at a predetermined distance from a corresponding hole. The dielectric material is preferably a ceramic comprised of BaO, TiO.sub.2 and ZrO.sub.2. If there is only one hole in the dielectric block, the input and output electrodes may be arranged around that hole. If there are two or more holes in the dielectric block, one electrode may be located near the hole at one end and the other electrode may be located near the hole at the opposite end of the dielectric block. The dielectric block is entirely plated with copper or silver with the exception of portions near each hole and the input and output electrodes. Each plated hole is essentially a coaxial resonator.

Abstract: Data muting apparatus is described that mutes variable-length data signals communicated between a central station and mobile and portable radios in a dispatch radio communications system. The central station includes a base station transceiver, a dispatcher console, a general communications controller (GCC), a digital communications computer and a display terminal. The base station transmitter and receiver communicate over an RF duplex channel to the transceiver of the mobile and portable radios. The dispatcher console provides for voice communications and is coupled by a transmit signal line and a receive signal line to the base station transceiver. The GCC provides for data communications and is also coupled to the transmit signal line and is interposed between the dispatcher console and the base station transceiver in the receive signal line. The GCC and mobile and portable radios include data muting apparatus enbodying the present invention.

Abstract: A system for radio-telephone communication between a user at a remote location and the commercial telephone system or between two users at remote locations comprises a fixed terminal that is connected by wire lines or the like to the commercial telephone system and a plurality of portable radio units. The terminal is equipped for duplex operation on a plurality of channels, each of which uses separate frequency bands for transmitting and receiving. Each of the portable units is a simplex transceiver adapted to receive on each of the frequencies of transmission from the terminal and to broadcast on each of the frequencies received by the terminal. The terminal places a channel acquisition tone on an unused channel that is the next to be used. The terminal calls portable unit by shifting channel acquisition tone to another channel and broadcasting an identifier to the portable unit.

Abstract: Apparatus is provided for inhibiting the generation of intermodulation products in a radio frequency amplifier coupled to a circulator. A control circuit generates a control signal exhibiting indicia of the amount of isolation provided by the circulator. The control signal is provided to a variable impedance synthesis circuit coupled to the circulation isolation port such that the impedance synthesis circuit exhibits the appropriate impedance to maximize circulation isolation. Intermodulation is thus minimized.