All-relay switch

A page from a North Electric brochure illustrating an all-relay type PABX.

An all-relay switch is a type of telephone switching system that connects calls by the use of relays only. An all relay switch does not use stepping switches, nor does it use power-driven devices of any kind. Advantages of an all-relay design were reduced maintenance, and quieter operation. Also, for exchanges of a relatively small size and call capacity, they were quite compact. Disadvantages were that an all-relay system had to be made larger to have the same number of links and trunks than a comparable step-by-step system. For this reason, they were usually used as PBX's or smaller exchanges.

An example of an all-relay type switch is the North Electric CX-100