Multiple tone signal system

Details Multiple tone signal system Multiple tone signal system

1981-05-04

1983-12-13

Pellinen, A. D.

Electrical audio signal processing systems and devices

Binaural and stereophonic

Broadcast or multiplex stereo

307524, H04H 500

Patent

active

044206585

ABSTRACT:
Multiple low frequency tones are employed for stereo indication in an AM stereo radio system. The tones are modulated on a carrier wave which is also multiplex modulated by stereo related audio signals. Detection of the presence of one of the tones in a received signal provides an indication of the possibility of stereo related modulation components in the received signal. Detection of the presence of both tones in the received signal provides confirmation that stereo related modulation components are in the received signal. In a preferred embodiment, 15 Hz and 30 Hz phase-related tones are used. A stereo receiver incorporates 15 Hz and 30 Hz phase detectors which form interrelated phase-locked loops with a 30 Hz reference oscillator. The presence of both tones in the proper phase relationship indicates reception from an AM radio station which is broadcasting in stereo.

REFERENCES:
patent: 3384824 (1968-05-01), Grenier
patent: 3518556 (1970-06-01), Holmboe et al.
patent: 3679832 (1972-07-01), Halpern
patent: 3980832 (1976-09-01), Nakamura et al.
patent: 4016366 (1977-04-01), Kurata
patent: 4087628 (1978-05-01), Sanders et al.
patent: 4165486 (1979-08-01), Yoshisato
patent: 4344038 (1982-08-01), Streeter

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