All-Relay Dial Systems

Special multicontact relays that close a large number of contacts at one time are used. The one-line diagram of Fig. 29 shows the basic principles of an all-relay system.

When a call is initiated by a subscriber in the thirties group shown, the finder F-30 "tens" multicontact relay operates, connecting all 10 lines of the group through to their "units" relays. If the calling line is line 35, the finder "units" relay 5 will be operated, thus connecting line 35 to the control relays. Dialing the desired number, for instance 37, will cause the connector "tens" relay (also a multicontact relay) C-30 and the connector "units" relay 7 to operate thus connecting lines 35 and 37. A 10-line system is shown in Fig. 29; however, this basic system is extended to serve larger numbers of lines.

Figure 29. An all-relay system for serving 10 lines.