Subscriber line circuit for telephone system - uses voice amplification network with transformer and threshold detector system

摘要

A circuit is used for subscriber allocation in a telephone network. It includes a transformer (4). The transformer has a ferrite core. There is an RC network and an emitter follower semiconductor (8) is connected across the primary rinding of the transformer. A rectifier circuit applying DC current to the subscriber line is connected across the secondary coil. The system input and output amplifier circuits (27) (32) are able to transmit vocal signals. A threshold detector (14) is used. It delivers signals having levels related to subscriber characteristics.