TEA1112; TEA1112A are low voltage versatile telephone transmission circuits with dialler interfaces. They have low DC line voltage, operating down to 1.6 V; voltage regulator with adjustable DC voltage providing a supply for external circuits; symmetrical high impedance inputs (64 kΩ) for dynamic, magnetic or piezo-electric microphones; asymmetrical high impedance input (32 kΩ) for electret microphones; DTMF input with confidence tone; mute input for pulse or DTMF dialling; receiving amplifier for dynamic, magnetic or piezo-electric earpieces; AGC line loss compensation for microphone and earpiece amplifiers; LED on-hook/off-hook status indication; microphone mute function.