Design Considerations for a CO-Powered Distributed-Drop PCM Station Carrier

A 24 channel pulse code modulation (PCM) station carrier system has been developed which is powered by the repeatered DS-1 span line and also possesses distributed-drop capability. These features were realized by bridge powering the span line repeaters and efficient power utilization at the subscriber terminals. The design philosophy behind this unique system capability is given along with an operational description of some key circuit designs. The resulting system offers unusual flexibility and very low per-channel cost. Even though the span line termination and powering is selfcontained, the system occupies about half the rack space of comparable systems. The system described is among the first to provide the qualities of digital transmission with the application versatilities and cost of analog station carrier.