TEA1112 Low-Voltage Telephone Transmission Circuit DIP-16 (TEA1112 IC)
The TEA1112 is a specialized bipolar integrated circuit designed for low-voltage telephone transmission. Housed in a 16-pin DIP package, it performs all the necessary speech and line interface functions for fully electronic telephone sets. It is specifically engineered to operate at very low line voltages (down to 1.6V), making it ideal for systems with long subscriber lines or those powered by parallel-connected telephone sets.
Commonly used in India for corded telephone repair and specialized communication interfaces, the TEA1112 includes an integrated dialer interface. This allows it to work seamlessly with both pulse and DTMF dialer ICs, providing a stable regulated voltage to power them directly from the telephone line.
Key Features
- Ultra-Low Voltage Operation: Maintains full functionality at a line voltage as low as 1.6V (excluding the polarity guard).
- Versatile Gain Adjustment: Features separate, adjustable gain settings for both the microphone (transmitting) and the earpiece (receiving) amplifiers.
- Dialer Interface: Provides a regulated supply voltage for external dialer ICs and includes a Mute input for dialing modes.
- Line Loss Compensation: Automatically adjusts transmission and reception gain based on the line current to ensure consistent audio quality.
- Symmetrical Inputs: Optimized for high-impedance microphones (such as electret types) to provide superior noise immunity.
- Integrated Stabilizer: Features an internal voltage stabilizer with an adjustable DC slope to match various exchange standards.
- Confidence Tone: Provides a side-tone during DTMF dialing so the user can hear the tones in the earpiece.
Specifications
- IC Type: Telephone Transmission and Speech Circuit
- Operating Line Current: 1 mA to 140 mA
- Minimum Line Voltage ($V_{LN}$): 1.6 V (Typical at 1 mA)
- Microphone Gain: 44 dB (Typical, adjustable)
- Earpiece Gain: 20 dB (Typical, adjustable)
- Internal Supply Voltage ($V_{CC}$): 2.4 V to 3.8 V
- Package Type: PDIP-16 (Through-Hole)
- Operating Temperature: -25°C to +75°C
Pinout Configuration (16-Pin DIP)
- Pin 1 (LN): Positive Line Terminal
- Pin 2 (GAS1): Transmitting Gain Adjustment 1
- Pin 3 (GAS2): Transmitting Gain Adjustment 2
- Pin 4 (QR): Receiver Output
- Pin 5 (GAR): Receiving Gain Adjustment
- Pin 6 (MIC-): Inverting Microphone Input
- Pin 7 (MIC+): Non-Inverting Microphone Input
- Pin 8 (STAB): Current Stabilizer
- Pin 9 (VEE): Negative Supply (Line Return)
- Pin 10 (IR): Receiving Amplifier Input
- Pin 11 (DTMF): Dual-Tone Multi-Frequency Input
- Pin 12 (MUTE): Mute Input (High for dialing mode)
- Pin 13 (VCC): Regulated Supply for Dialer
- Pin 14 (REG): Voltage Regulator Decoupling
- Pin 15 (AGC): Automatic Gain Control Input
- Pin 16 (SLPE): DC Resistance (Slope) Adjustment
