Voltage-Monitoring ICs

Voltage monitoring ICs enable many features of VOIP and IP PBX tip-and-ring telephone systems, including line-in-use detection, caller ID, and imperceptible voice recording. The integrated circuits use a high-impedance resistor divider to detect differences between the common mode voltage and other input currents. Currents with differing voltages get routed to switches while the IC creates a scaled representation of phone line voltages and outputs polarity information. The IC does this while generating virtually no noise across the circuit.