Abstract: An arrangement for releasably retaining a telephone apparatus in a standby condition includes a handset including an earpiece and a base having a shelf portion for receiving the earpiece. A hooking post member protrudes through the shelf portion and includes an integral spring to enable the hooking post member to be resiliently movable towards and away from the shelf portion. A switch hook which is separate from the hooking post is arranged to be actuated by the earpiece when the earpiece is brought into engagement with the base. When the earpiece engages the base shelf portion, the hooking post member is resiliently urged into contact with the earpiece for releasably retaining the earpiece on the base. A guide on the base prevents the hooking post member from twisting or rotating.

Abstract: A helical filter is disclosed which includes a ground plane having microstrip transmission line segments to which a respective helical resonator coil is connected at the high impedance end thereof. A discrete capacitor is connected in parallel with each transmission line. A housing is provided with individual resonator compartments which effect associated distributed capacitance with the resonators themselves, which capacitance may be adjusted by included tuning screws. Conductors are connected to and form an integral part of a given two of said transmission lines and serve as the input and output for the helical filter. The transmission line and discrete capacitor pair provides the necessary impedance match, while the capacitor itself facilitates temperature compensation and frequency range selection.

Abstract: An improved fault detect algorithm and circuit is disclosed which quickly evaluates substantially all the elements within a successive approximation A/D convertor without resorting to off-line measurements. This method utilizes a small alternating offset signal injected into the correction loop in addition to the already converted value to determine whether the elements within this loop are operating properly for any in range analog input value.

Abstract: An alphanumeric entry system which is provided with an electronic lock-out feature. The keypad entry system of the present invention comprises an alphanumeric keypad having function keys and display, a microprocessor, and an electronically programmable read-only memory device. The display consists of a series of system related menus as well as an alphanumeric display area. One of the system related menus corresponds to a locking feature, which may be activated by a general purpose function key. In the locking mode, the radio keypad toggles between a locked and unlocked condition as controlled by the function keys in accordance with a predefined sequence. The alphanumeric entry system of the present invention is particularly advantageous for use with portable two-way communications equipment which operate in a plurality of radio systems.

Abstract: A method and apparatus for coordinating the transfer of communications control from one independent radio communications system to another is disclosed. A remote unit which communicates data messages is associated with a home system which has a plurality of fixed sites and overlapping radio coverage areas. As the remote unit travels away from its home system, communications may be maintained by providing radio coverage from an independent roam system. The last message received by the home and roam systems from the remote unit has the associated radio signal strength and time of reception stored at each system. When a current message is transmitted by the remote unit and both the home and the roam system receive the message, the roam system time stamps the message and calculates the signal strength associated with the current message.

Abstract: A maximum distance from zero-crossing demodulation method for MSK or OK-QPSK signals is disclosed which utilizes the zero-crossing information for establishing a bit edge reference and an optimum sampling point situated essentially midway between the zero-crossings of the higher of the two incoming signalling tones. This method is able to provide improved noise immunity over other known methods by at least an additional 10 degrees of phase margin while conserving processor steps during the phase detection process.

Abstract: An optimized method of bus contention comprising monitoring the bus for an idle or busy bus condition and either attempting an asynchronous bus access if the bus is idle or synchronously attempting a prioritized retry after a busy bus condition is sensed, after a bus access collision is sensed, and upon initial power-up, synchronized to the current message completion. The prioritization comprises a constant time delay plus a bit-time delay proportional to said accessing device's address identification.

Abstract: Disclosed is an error corrector for a linear feedback shift register sequence employing an open loop linear feedback shift register (LFSR) having selected bits "tapped" and combined to form a feedback signal. The taps implement an orthogonal convolutional code that is inherently redundant, therefore, the transmission of parity bits is not required. The feedback signal is combined with the received synchronization signal to form an error estimate that is temporarily stored in a syndrome register. By majority voting a selected outputs of the syndrome register a reliable determination of a received error can be made. Once an error determination is made, a correction signal is generated to correct the bit in error thereby providing a high probability of initiating and maintaining synchronization.

Abstract: A method within adjusting values of a passive temperature compensation network for use in an oscillator includes the steps of determining the frequency variation of the oscillator from nominal over a specified temperature range, determining the maximum frequency variation over the temperature range, and recalculating the performance of the circuit over the temperature range utilizing reduced values for the temperature compensation components therein. The oscillation frequency can be utilized as the controlled parameter to a laser based component trimming system. Power is applied to the oscillator and the compensation component is trimmed until the circuit oscillates at the specified target frequency.

Abstract: The remote control system having symmetrical signaling circuits for radio communications is coupled to a single wire line/audio channel and permits two or more units, base stations and/or remote consoles, to be coupled to the single wire line. Each signaling circuit comprises a wire line coupler for coupling to the wire line, an audio input line and an audio output line. An automatic gain control circuit is coupled between the wire coupler and the audio output line and a filter and line driver are coupled between the audio input line and the wire coupler. A control unit including a microprocessor, a tone encoder, a tone decoder, a timer, a clock, and a memory is coupled by output lines to the automatic gain control circuit for controlling the modes of operation thereof which include a slow decay mode, a fast decay mode, an adapt mode and a hold gain mode. The output from the gain control circuit is also routed through a band pass filter and a limiter to the control unit.

Abstract: A mobile radio receiver employs an SAW filter to provide an appropriate time delay to enable an extender to effectively blank the recovered signal thereby preventing noise from entering the IF section of the radio. The SAW filter allows long signal delays without significant pulse stretching while also allowing narrow IF bandwidths. The control pulse to the blanker switch is shaped to reduce the coupling of noise generated within the blanker switch from the received signal path. The operation of the extender is controlled by the main receiver through an AGC signal to determine when, and to what extent, the extender is enabled.

Abstract: A method and means for improving the frequency resolution in a digital oscillator is described. According to the principles of the present invention, a digital oscillator may be comprised of a frequency latch, a phase accumulator, and a ROM based waveform generator. Improved frequency resolution is achieved in the digital oscillator, without increasing ROM size by quantizing the summed output of a dither generator and the phase accumulator before sending the resultant multi-bit signal to a ROM. The contents of the ROM are sequentially addressed with the resultant multi-bit signal. The output of the ROMs comprise digital words corresponding to a desired waveform envelope.

Abstract: A receiver for frequency modulated signals, having down-conversion to a baseband, zero intermediate frequency for selectivity, followed by up-conversion to a non-zero IF for amplification, limiting, and demodulation.A phase-lock loop locks the frequency of the down-conversion source to the center frequency of the signal coupled to the baseband IF, converting the signal to precisely zero frequency. This avoids the beat note often found in direct conversion systems. The phase-lock loop additionally provides inherent demodulation of the FM signal.The received FM signal is coupled to the baseband IF through a radio frequency amplifier for improved sensitivity and local oscillator isolation, or through a first IF comprising a mixer, local oscillator, filter, and amplifier.

Abstract: A multiplexing arrangement is described for use in a digital communications system, in which it is desired to multiplex plural user data inputs into a single serial digital communications channel and then to decode the data to the appropriate user data outputs. The arrangement contemplates the transmission of data in blocks of n.sup.2 bits, and provides framing in the form of a frame alignment word having the value of F for n bits, followed by n-1 subsequences each of n bits duration and each initiated by a framing bit having the value of F-bar, with the last subsequence terminating with a framing bit having the value of F-bar. The implementation is simple and provides rapid acquisition of the framing. In principle, the framing is error free in not being affected by the values assigned to the data.

Abstract: The invention provides a clock recovery circuit for deriving a recovered clock signal from the band limited multi-level digital signal. The multi-level digital signal is compared with a number of reference levels in a bank of comparators whose outputs are combined to provide a marking signal indicative of threshold crossings by the multi-level signal. The marking signal consists of groups of transition markers separated by eye intervals. A signal source provides clock pulses and window pulses with the window pulses being synchronized with the eye intervals to provide a recovered clock signal.The invention may be implemented entirely in digital form and is particularly suitable for use in partial response signalling in which band limited multi-level digital signals are transmitted without additional clock signals. Performance may be further enhanced by utilizing a smoothing phase locked loop to provide a smoothed clock signal.

Abstract: A rechargeable high energy density cell having a metal--metal oxide negative electrode, more specifically, the metal being cadmium, wherein the metal is in the form of thin flakes. Such cells show improved energy density and cycle life when charged-discharged at higher rate and to 100% depth of discharge.

Abstract: In accordance with the present invention, there is provided a method of substantially flattening the modulation response in a frequency synthesizer. The method includes the steps of generating a synthesized frequency in response to a filtered control signal; scaling the synthesized frequency with a scalar; generating a control signal, having a response substantially the reciprocal of the frequency generation response, and indicative of the phase relationship between a reference frequency and the scaled, synthesized frequency; and filtering the control signal, whereby the interaction of the phase relationship control signal response and the frequency generation response approximates a flat modulation response.

Abstract: A device for monitoring temperature as a function of electrical resistivity comprises a sensing element formed of a ceramic including lanthanum chromite with a dopant selected from magnesium oxide, aluminum oxide, titanium oxide and silicon oxide, and having electrodes operably affixed to the surface thereof.