Electronically-switched multifrequency generator with transducer control

Abstract From the Canadian patent

Abstract of the Disclosure In a multifrequency generator providing tone signaling for a telephone, the common switching functions are performed by solid state switching circuitry. Improved signal transfer between the telephone line and transmit and receive transducer of the telephone is provided by arranging the solid-state transmit and receive switches in a gain configuration to increase the level of the speech signal. The tone signals are digitally synthesized and use an integrated R-C oscillator as a reference. Button down and button up debouncing or a contact closure signal from a single contact per button keypad is provided.