Motorola Corporation

Robert R Bell

Scott T Christians

A radio transceiver is disclosed having manual controls on a microphone and the remainder of the circuitry located in a main chassis. The microphone and chassis are connected by means of a multiconductor cable, and time sharing multiplexing techniques are utilized and serially transmit information, bidirectionally, along a common data line while a clock line is utilized to synchronize the operation of main chassis and microphone circuitry. Multiple bit binary coded digital words are sent to the microphone to activate microphone displays while analog signals are sent from the microphone to the main chassis to provide analog control signals for the transceiver. A digital synchronizing pulse detector is disclosed for use in the above transceiver multiplexing system. The detector identifies synchronizing pulses which occur in the clock signal wherein the identification insures the synchronization of microphone and main chassis circuitry. The transceiver provides for designating a subset of all of the available communication channels as desired channels, and in a memory mode the transceiver is tuned only to those desired channels. Distinctive visual displays are produced indicating if any channels have been designated as desired channels, and if all possible storage space for storing desired channel identification has been utilized. In addition, the dual use of a few pushbuttons is disclosed such that the sequence in which these pushbuttons are actuated determines the transceiver mode of operation selected.

Digital receiver/transceiver synchronization pulse detector for a

Transceiver/receiver information multiplexing system

A frequency synthesizer for a citizens band transceiver is disclosed. The synthesizer utilizes a single master crystal oscillator whose output is coupled to a difference mixer that receives the output of a voltage controlled oscillator (VCO) and provides an input to a programmable frequency divider. This programmable divider provides an output to a phase-frequency comparator which commpares this signal to a reference signal supplied by a fixed divider coupled to the master crystal oscillator. The comparator output, through a low pass filter, controls the voltage controlled oscillator output. The VCO output signal is substantially higher than the maximum frequency capability of the programmable frequency divider, and the present invention by utilizing the master crystal oscillator and difference mixer provides an inexpensive frequency synthesizer utilizing a programmable frequency divider having relatively low maximum input frequency capabilities, and this accomplished without the use of costly multiplier circuits in the frequency synthesizer.

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Libertyville, IL, United States of America

Robert R Bell