B-cubed Engineering, Inc.

Motorola Corporation

Stephen Michael Bench

William R Dirkes

James C Secora

Manohar A Joglekar

Michael A Stepien

Manohar A Juglekar

Michael A Stephen

A data communication system for use in the control and monitoring of mobile stations, for example, in a bus monitoring system, from a central station over a communication channel carrying both data and voice information. Information is encoded into digital messages having a start code followed by one or more data blocks. The start code identifies the beginning of the data block that follows and enables synchronization of clock circuitry to the received data frequency. The data blocks have N digital words with M binary bits where one word is a parity word and N-1 words are data words. Each of the data words has a data portion and parity portion coded for correction of at least one error. Reliability is enhanced by a data detector which discriminates between data and noise or voice to provide an indication of the presence of data. In transmitting the digital messages, the bits of the N words in each data block are interleaved to provide protection against error bursts.

Clock circuitry for a data communication system

Data communication system with random and burst error protection and

The disclosed circuit provides a signal generator which is particularly adapted for use as an audible 'kilo-sonic' game device in which a plurality of switches are provided so that the different combinations of switch positions produce a corresponding number of different sounds. The circuit includes a voltage-controlled-oscillator (VCO) having an output coupled to a transducer such as a speaker. The VCO is modulated in accordance with a control signal, provided by an up-down staircase generator which is responsive to a pulse generator, to vary the frequency of its output signal. The output of the pulse generator is also selectively coupled with the output of the staircase generator. Time-constant circuits in each of the generators are respectively under the control of selected ones of the switches; and two basic modes of operation are provided by the selected switches so that the control signal at the VCO input is either a pseudo random signal, or a synchronized sub-multiple signal wherein the frequency of the staircase generator output signal is a sub-multiple of the pulse generator output signal. Accordingly, the number of different output sounds provided by the disclosed circuit is geometrically proportional to the number of switches provided.

Dual-mode waveform generator

A dynamic expander which is particularly suitable for restoring the original dynamic range of prerecorded stereo sound program material is disclosed. In this embodiment, the expander comprises first and second variable gain amplifiers respectively coupled to a stereo input. The gain of the amplifiers is controlled by a common slow-attack, slow-decay time-constant circuit. An input of the time-constant circuit is coupled to the stereo input and the time-constant circuit responds thereto to provide a control signal which is indicative of the volume of the program material but which varies in accordance with the characteristics of a non-linear element in the time-constant circuit and with the slow-attack and slow-decay characteristics of the time-constant circuit. The control signal of the time-constant circuit drives a light-emitting-diode (LED) which, in turn, determines the resistance of a pair of matched, light-controlled-resistors (LCR's). Each LCR acts linearly and controls the gain of a respective one of the variable gain amplifiers in accordance with the resistance of that LCR.

Dynamic expander

The disclosed circuit provides a wideband, wide-range logarithmic responding voltmeter particularly suitable for use as a transducer analyzer. The circuit includes an input for receiving a given A.C. input signal which can vary within a 100 db dynamic range. The input signal is coupled to a buffer amplifier the output of which is capacitively coupled to a logarithmic converter. The converter includes an operational amplifier and provides an A.C. output signal which is proportional to the logarithm of its A.C. input signal. The open loop gain of the operational amplifier is utilized to provide the A.C. output signal. The output signal of the converter is capacitively coupled to a precision AC/DC converter which rectifies and filters the output signal to provide a D.C. output voltage the level of which is, therefore, also proportional to the logarithm of the given A.C. input signal within its 100 db range. The D.C. output voltage is coupled to utilization means such as a logarithmically calibrated chart recorder or meter. The precision AD/DC converter also includes a zero-adjustment for nulling any offsets in its circuit and any residual noise at the output of the logarithmic converter. Accordingly, with no input signal applied to the disclosed circuit the output recorder and/or meter stably read exactly zero ('0').

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Lake Zurich, IL, United States of America

Stephen Michael Bench