Two-tone attention signal broadcasting system

Details Two-tone attention signal broadcasting system Two-tone attention signal broadcasting system

1976-08-04

1978-07-25

Griffin, Robert L.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

325 39, 325 55, 325364, 325341, 340164B, H04H 900

Patent

active

041032357

ABSTRACT:
To broadcast a two-tone attention signal to receivers, a two-tone generator includes an interrupt switch, which, when a button is depressed, interrupts the audio signal from a broadcasting station and instead applies two combined frequencies which have been generated to the broadcast audio chain to modulate the carrier with the two-tone attention signal and broadcast it. To generate the two frequencies, a single clock frequency is applied to two different frequency dividers which digitally divide the clock frequency into the desired two tones. The two frequencies from the two dividers are applied to sine-wave generators which first differentiate the pulses from the digital circuits and then apply them to tank circuits. The time duration of the two signals is controlled by a digital system which counts 60 Hertz pulses for a predetermined time period after the button is depressed prior to terminating the two-tone attention signal. The receiver-decoder includes a ready lamp that is illuminated by the audio from the station, a timer similar to the timer used in the transmitter, and an automatic reset circuit that is delayed from the turn on time of the receiver-decoder.

REFERENCES:
patent: 2671167 (1954-03-01), Kulansky
patent: 3535636 (1970-10-01), Muilwijk
patent: 3676780 (1972-07-01), Niemann et al.
patent: 3714595 (1973-01-01), Denenberg et al.
patent: 3772241 (1973-11-01), Grosser et al.
patent: 3845391 (1974-10-01), Crosby
patent: 3909722 (1975-09-01), Bennett Jr.,
patent: 4010460 (1977-03-01), Derosa

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