Monolithic loop and ringing current supply circuit for telephony - has four wire incoming line amplifier modulating two=wire current via controlled current source

摘要

The supply circuit has the 4-wire line's (ADS) incoming amplifier (Van) connected at its output both to a supply unit (EE) and via a filter (NB) to the input of the 4-wire lines outgoing amplifier (Vab, RV2). The 2-wire line (2DS) is connected by both wires to the two inputs of the 4-wire's outgoing amplifier. The supply unit contains voltage sources for OV and -60V and is connected between the two 2-wire wires. Transformers and relay contacts avoided. Heat dissipation is low.