Low DC line voltage; operates down to 1.6 V Line operation current range 10...140 mA Icc 1.35 mA
Voltage gain range:

microphone amplifier 11...52 dB

telephone amplifier 20...31 dB
Voltage regulator with adjustable static resistance Provides supply for external circuits Symmetrical high-impedance inputs
(64 k ) for dynamic, magnetic or piezoelectric

microphones
Asymmetrical high-impedance inputs

(32 k ) for electret microphones
DTMF signal input with confidence tone
Mute input for pulse or DTMF dialing
Receiving amplifier for dynamic, magnetic or piezoelectric

earpieces
Large gain setting range on microphone and earpiece

amplifiers