Addition and subtraction of relay channels to transmission system - is effected in frequency multiplexed transposition system without affecting direct channels

摘要

Telephonic channels are transmitted on a single coaxial cable with repeaters using frequency division multiplexing. In one direction a lower frequency band is used while a higher frequency band is used in the other direction. Direct and omnibus channels are available. The omnibus channel groups can be added or removed without loss of the corresponding frequency band and are obtained using a derivation circuit coupled (40, 41) to the transmission line (5). Each input is connected to an amplifier (42, 52) followed by a coupler (43, 53) permitting connection (44, 54) to the omnibus channels of the lower (44) or upper (54) frequency band. The couplers are followed by filters (46, 56) and amplifiers (47, 57) which with the input amplifiers (42, 52) permit compensation for direct channel attenuation. A second coupler (49, 59) receives inputs (50, 60) from the omnibus channels.