Public address/radio switching system

Details Public address/radio switching system Public address/radio switching system

1975-02-10

1976-02-10

Mayer, Albert J.

325 22, 179 1A, 179 1C, 179 1SW, 179 2E, H04B 140

Patent

active

039380432

ABSTRACT:
Public address add-on circuitry to a conventional radio includes a microphone coupled to a preamplifier which draws significant idle current, and is optimally operable when coupled to a proper load resistance. Permanently affixed and capacitively coupled to the audio input stage of the radio is a series element containing a semiconductor junction device and a resistor selected to properly load the microphone preamplifier. When switching from radio operation to public address the quiescent current of the microphone amplifier reduces the resistance of the junction from a high to a low value thereby allowing the preselected resistor to load the microphone. Semiconductor action further disables the tuner portion of the receiver.

REFERENCES:
patent: 2766378 (1956-10-01), Sundin et al.
patent: 3365546 (1968-01-01), Kemper
patent: 3382321 (1968-05-01), Lybarger et al.

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