General Electric Company

James H Elder

Hubert A Patterson

William C Agnor

Apparatus and method for programmably phase shifting an audio tone is disclosed for use in a cellular communications system. A digital phase lock loop (PLL) includes a programmable phase shift therewithin and an audio output, phase-shifted from an input audio tone, is extracted from the thus programmed PLL. The apparatus of the present invention is particularly designed to be realized using digital circuits capable of integration into a monolithic CMOS IC.

Digital apparatus and method for programmably phase shifting an audio

A paging receiver selectively operable in either a six tone battery saving mode or in a five tone non-battery saving mode. The receiver features a serial code plug for programming a programmable tone detector to be responsive to a specific paging receiver address comprising a predetermined combination of preamble and paging signals. The use of a serial code plug in place of the parallel code plug previously known and utilized in the industry allows a reduced complexity of the paging receiver and a corresponding size, weight and cost savings.

Paging receiver having a serial code plug

Binary messages received over a radio channel are subject to fading or noise degradation because of the radio channel. Accordingly, a predetermined binary preamble followed by a synchronizing word are transmitted ahead of the message. In order that the synchronization be correct, the end of the preamble should be determined as accurately as possible. This is achieved by fast and slow detectors which receive the preamble. The fast detector output is applied to a time delay. The slow detector and the time delay outputs are applied to an output circuit which produces an output signal in response to the slow detector and the time delay outputs both being present. The fast and slow detectors and the time delay are arranged so that the output signal is produced at the desired time after the preamble begins, thereby accurately indicating when the synchronizing word is to begin.

Message preamble detector

In radio communication systems transmitting voice and data, data is frequently transmitted at the beginning of the transmission, and this may then be followed by voice. The sound of the data in the receiver loudspeaker is unnecessary and often annoying. This sound is eliminated by a muting circuit which initially mutes the receiver for a predetermined time following receipt of a carrier signal, and then mutes the receiver when data is detected. After the data ends, the receiver is unmuted if a carrier is still present.

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Brookneal, VA, United States of America

James H Elder