Transmission system for carrier signals - has two switches operated by control criteria for reception and sending

摘要

The system operates on the segregated band method, and comprises a sender and a receiver for signals in different frequency positions. The sender can be set by a control device to one of the two frequencies, and a four wire line can be connected to the sender or receiver through switches operated by the control device. The signals are esp. transmitted by the two-wire separated band method, and the four-wire terminals are connected through directional filters to a two-wire terminal. When the control device receives a call signal, it delivers a first control criterion, and when it sends a call signal, it delivers a second criterion. The switches (72, 73) are in one position during a first criterion and in the other position during the other criterion.