TEA1064A

Low voltage versatile telephone transmission circuit with dialler interface and transmit level dynamic limiting

GENERAL DESCRIPTION

The 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