GENERAL DESCRIPTION
The TEA1064B 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. 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
• 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 dynamic, magnetic 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
• MUTE, POWER-DOWN and DTMF input reference (pin VEE2) can be connected either to VEE1or SLPE.