Abridgment of carrier telephone system for short toll circuits

This paper describes a new carrier telephone system which is designed for use in the telephone plant as a substitute for open-wire line construction for circuits of shorter lengths than could be economically spanned by multi-channel types of carrier systems in use for longer distance transmission. This new system, which is known as the type D carrier telephone system, provides one additional talking circuit per pair of wires. The equipment is adapted to provide facilities quickly, and is capable of being moved readily from one location to another when temporary facilities are desired. The system employs a novel and original modulation circuit which is fully described in the complete paper.