Abstract: Improved method and apparatus in the form of coherent demodulators for MSK signal or other angle-modulated carrier signals of substantially constant amplitude and continuous phase are provided. The coherent demodulators include a frequency doubler, a first mixer for multiplying the frequency doubled signal with a half clock signal to produce a carrier term signal, a bandpass filter for filtering the carrier term signal and a divider coupled to the carrier bandpass filter to produce a coherent carrier signal. The half clock signal is generated by multiplying the frequency doubled signal with the filtered ouput signal of the carrier bandpass filter by a second mixer, and bandpass filtering the output signal of the second mixer to produce the half clock signal. The received binary data modulated signal and the generated coherent carrier signal are input to a quadrature detector for recovering the binary data.

Abstract: Digital circuitry adaptable for controlling dwell in a spark and dwell ignition control system is disclosed. Maximum advance and reference sensors are utilized to produce pulse transitions which determine positions of maximum and minimum possible advance for spark ignition with respect to the position of the engine crankshaft. For each maximum advance sensor pulse transition a main counter starts a sequential running count of speed independent clock pulses wherein the maximum count obtained by the counter is related to engine crankshaft speed. The running and maximum counts of the main counter are utilized by dwell circuitry to determine the time prior to the next maximum advance pulse at which spark coil excitation should occur.

Abstract: An improved header and housing assembly for holding a miniaturized electronic circuit module having a plurality of leads includes a header member having a plurality of apertures arranged to accept the leads of the module. A jaw mechanism associated with each aperture captivates the leads and a protective housing encloses the module between the header member and the housing. An interconnection board which is mounted to a flexible printed circuit board engages the header and housing assembly and forms a base permitting the assembly to be mounted to the flexible circuit board.

Abstract: A paging device and supporting receptacle are provided for detachably securing the device to an article of clothing and providing for limited pivotal movement of the device to permit visual observation of a display portion of the device without completely removing the device from the receptacle.

Abstract: A protective power foldback circuit which protects a power semiconductor device from damage resulting from variations in load, supply voltage, and input drive power is disclosed. When the supply voltage exceeds a certain value, the drive power to the power device is reduced in an amount greater than that produced by the excess supply voltage thereby protecting the power device from the combined effects of load, supply voltage, and drive power.

Abstract: A diversity signal strength indicator for transmission site selection in a cellular-like mobile radio system produces an output strength indication signal which is proportional to the logarithm of the average strength of two diversity input signals. The two input diversity signals are time multiplexed together to form a composite signal, and a log amplifier/envelope detector then produces an intermediate log signal which is proportional to the logarithm of the envelope of the composite signal. The intermediate log signal is then operated on by a peak detector to produce a peak intermediate log signal which is then passed through a low pass filter to produce an output strength detection signal proportional to the average of the intermediate log signal and thus proportional to the logarithm of the average strength of the diversity input signal.

Abstract: A two-channel audio amplifier for use in a vehicle sound system is provided. Each channel drives a pair of loudspeakers and includes a common amplifier connected to drive one terminal of each speaker. The remaining speaker terminals are connected to the outputs of a pair of additional amplifiers. Signals of one phase are applied to the common amplifier. Signals of opposite phase are applied to the additional amplifiers. Signals in phase with the common amplifier are applied to the inputs of the additional amplifiers through field-effect transistors. Control signals applied to the control electrodes of the transistors control the magnitude of the applied in-phase signal to independently control the output level of the speakers.

Abstract: An MOS crystal controlled oscillator circuit is provided which includes a pair of MOS transistors coupled together in complementary fashion to form a first non-inverting stage. The output of the first non-inverting stage is coupled to the input of a second non-inverting stage including a MOS transistor exhibiting a source follower configuration or a bipolar transistor exhibiting an emitter follower configuration. The output of the second non-inverting source follower stage is coupled via a feedback element, for example, a piezoelectric crystal, to the input of the first non-inverting stage. A feedback loop is thus formed which causes the circuit to resonate at a frequency determined by the piezoelectric crystal feedback device. This oscillator configuration results in a degree of insensitivity to variations in parasitic impedance of the piezoelectric crystal feedback device.

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 data communications system is described that covers a geographic area divided into a plurality of non-overlapping zones and includes a general communications controller (GCC), a plurality of channel communications modules (CCM) and associated transmitters and receivers, and a plurality of portable radios. Message signals carrying alphanumeric information are communicated between the GCC and the portable radios by way of a radio channel. Each CCM takes a signal strength measurement every time it receives a message signal from a portable radio. The GCC gathers the signal strength measurements from the CCM receivers receiving the same message signal and computes an adjusted signal strength for each zone. The GCC then selects the zone having the largest adjusted signal strength for determining the location of the portable radio that transmitted the message signal.

Abstract: A single carrier is amplitude-modulated by a signal which is a transform (as the sine function) of the audio signal, and one set of sidebands is removed. In a receiver, the signal can be recovered by first deriving the Hilbert transform of the sine transform, and multiplying it by the signum of the derivative of the original audio signal to obtain the cosine transform. The sine and cosine transforms are then decoded to obtain the original audio signal.

Abstract: A current mirror circuit comprising a first current mirror circuit with a first error correction transistor connected between the base and collector of the first transistor of the first current mirror; a second error correction transistor connected to the first error correction transistor and a second current mirror circuit connected to an input current source and the base of the second error correction transistor. The second error correction transistor samples the signal from the collector of first error correction transistor and feeds its base current, which is almost equivalent to the base current of the first error correction transistor, to the input of the second current mirror circuit. The second current mirror circuit combines the input current source current with the base current of the second error correction transistor and generates a current which is fed to the collector of the first transistor of the first current mirror circuit.

Abstract: This invention is directed to an AT-cut quartz resonator having two different resonant modes simultaneously occurring in which a generally rectangular polyhedron has first and second electrodes disposed on opposing faces, and having the width to height selected within the range of 8 to 25. The width is selected such that a thickness shear mode and flexure mode are simultaneously excitable and coupled together. The AT rotation angle is selected so that a first signal responsive to the coupled flexure mode and thickness shear mode has a substantially cubic frequency versus temperature response over a desired temperature range and a second signal responsive to the coupled flexure and thickness shear modes has a substantially linear frequency versus temperature response over the desired temperature range.

Abstract: Improved temperature compensated, automatic output control (AOC) circuitry for RF signal power amplifiers is described that maintains the output power within one-half dB of a selected one of eight power levels varying from nine milliwatts to five watts, a dynamic range of twenty-eight dB. The amplification of the RF signal amplifier is proportional to a drive current signal provided by a current amplifier. A half-wave rectifier is coupled to the output of final amplifiers for generating an output power signal that has a magnitude proportional to the output power. The half-wave rectifier is temperature compensated for and biased by a diode coupled to the rectifier by one resistor and coupled to supply voltage by another resistor. The output power voltage is further coupled to an amplifier having an amplification factor selected by level control signals.

Abstract: Improved control circuitry for pulse-width-modulated power supplies is described that includes a pulse generator for generating a train of trigger pulses at a predetermined repetition frequency, a signal source for generating a reference voltage and a comparator for comparing the power supply output voltage to the reference voltage and generating a first state of a switching control signal in response to each trigger pulse from the pulse generator and a second state of the switching control signal when the magnitude of the power supply output voltage is equal to the magnitude of the reference voltage. The first state of the switching control signal enables switching transistors of the switching power supply, and the second state of the switching control signal disables the switching transistors. The comparator also includes circuitry for reducing the magnitude of the reference voltage when the switching control signal has the second state.

Abstract: A radio paging device is provided which includes apparatus for preventing turn off of the paging device until all selective calling message signals which are stored in the pagers memory have been displayed. The pager of the present invention further includes apparatus for automatically initiating interrogation of the memory when the user attempts to turn off the paging device.