GENERAL DESCRIPTION
The TEA1064A is a bipolar integrated circuit that performs all the speech and line interface functions required in fully electronic telephone sets. It performs electronic switching between dialling and speech and has a powerful DC supply for peripheral circuits. The IC operates at line
voltages down to 1.8 V DC (with reduced performance) to facilitate the use of more telephone sets connected in parallel. The transmit signal on the line is dynamically limited (speech-controlled) to prevent distortion at high transmit levels of both the sending signal and the sidetone.

FEATURES
• Low DC line voltage; operates down to 1.8 V (excluding polarity guard)
• Voltage regulator with low voltage drop and adjustable static resistance
• DC line voltage adjustment facility
• Provides a supply for external circuits in two options:
unregulated supply, regulated line voltage;
stabilized supply, line voltage varies with supply
current
• Dynamic limiting (speech-controlled) in transmit direction prevents distortion of line signal and sidetone
• Symmetrical high-impedance inputs (64 kΩ) for dynamic, magnetic or piezo-electric microphones
• Asymmetrical high-impedance input (32 kΩ) for electret microphones
• DTMF signal input
• Confidence tone in the earpiece during DTMF dialling
• Mute input for disabling speech during pulse or DTMF dialling
• Power-down input for improved performance during pulse dial or register recall (flash)
• Receiving amplifier for magnetic, dynamic or piezo-electric earpieces
• Large amplification setting ranges on microphone and earpiece amplifiers
• Line loss compensation (line current dependent) for microphone and earpiece amplifiers (not used for DTMF amplifier)
• Gain control curve adaptable to exchange supply
• Automatic disabling of the DTMF amplifier in extremely-low voltage conditions
• Microphone MUTE function available with switch