Tone calling with single sideband radio equipment

Details Tone calling with single sideband radio equipment Tone calling with single sideband radio equipment

H - Electricity

04

B

379/11, 325/30,

H04B 1/04 (2006.01) H04B 1/30 (2006.01) H04Q 7/10 (2006.01)

Patent

CA 1049616

ABSTRACT OF THE DISCLOSURE Tone calling equipment for radio telephones employing a single sideband radio frequency transmitter to transmit a double tone signal comprising two precisely spaced side tones. These side tones are at frequencies fc + f1 and fc - f1, produced by modulating an audio tone f1 on a subcarrier audio signal at fc. The two side tones are modulated by a single sideband transmitter onto a radio frequency (RF) signal and are then both transmitted. At a single sideband RF receiver, the two side tones are received as an RF signal. The absolute value of this signal may vary, but the two side tones are separated by precisely 2f1. The difference 2f1 between the two side tones is detected, thus eliminating the variable errors which may be present in the detected signal, and enabling the use of a very narrow filter. This filter passes the signal 2f1 to provide an output audio tone which actuates, for example, telephone ringing apparatus.

206828

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