The MC34114 is a monolithic integrated telephone speech network designed to replace the bulky magnetic hybrid circuit of a telephone set. The MC34114 incorporates the necessary functions of transmit amplification, receive amplification, and sidetone control, each with externally adjustable gain. Loop length equalization varies the gains based on loop current. The microphone amplifier has a balanced, differential input stage designed to reduce RFI problems. A MUTE input mutes the microphone and receive amplifiers during dialing. A regulated output voltage is provided for biasing of the microphone, and a separate output voltage powers an external dialer, microprocessor, or other circuitry. The MC34114 is designed to operate at a minimum voltage of 1.2 volts, making party line operation possible.
A circuit using the MC34114 can be made to comply with Bell Telephone, British Telecom (BT), and NTT (Nippon Telegraph & Telephone) standards. It is available in a standard 18-pin, and a 20-pin SOIC (surface mount) package.
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