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.
The Philips TEA1112 and TEA1112A are bipolar integrated circuits designed to perform all speech and line interface functions required in fully electronic telephone sets, cordless telephones, fax machines, and answering machines. These low voltage versatile circuits operate with a DC line voltage down to 1.6 V and facilitate the use of telephone sets connected in parallel.
The ICs provide electronic switching between speech and dialling, featuring symmetrical high impedance inputs for dynamic, magnetic, or piezo-electric microphones and asymmetrical inputs for electret microphones. Key functions include a DTMF input with confidence tone, a receiving amplifier with AGC line loss compensation, and an LED driver for on-hook/off-hook status indication. The microphone amplifier can be disabled via a mute function to enable DTMF dialling.
| Minimum DC line voltage | 1.6 V |
|---|---|
| Microphone input impedance | 64 k Ω |
| Electret microphone input impedance | 32 k Ω |
| Typical voltage gain (microphone amplifier) | 51.8 dB |
| Typical voltage gain (receiving amplifier) | 19.2 dB |
| Maximum LED supply current | 19.5 mA |
| Preferred R SLPE value | 20 Ω |
These circuits are used in line powered telephone sets, cordless telephones, fax machines, and answering machines.
The ICs operate at a line voltage down to 1.6 V DC, though performance is reduced at this level.
The microphone amplifier can be disabled by activating the microphone mute function when the MMUTE pin is LOW.