CROSSBAR DIAL TELEPHONE SWITCHING SYSTEM 



87 



Multi-Contact Relay 



The multi-contact relay used in the crossbar system is shown in 

 Fie:. 5. It resembles in design the vertical unit of a crossbar switch. 



% 



Fig. 5 — Multi-contact relay. 



The relay is provided in four sizes in respect to the number of contacts, 

 namely, in 30, 40, 50 and 60 sets of individually insulated contacts, 

 all of which are of the normally open type which are closed when the 

 magnets of the relay are operated. Each relay is provided with two 

 separate magnets, armatures and associated groups of springs, and 

 both magnets are energized in parallel in order to close all of the 

 contacts. By operating the two magnets independently the structures 

 can be used as two separate relays, each equipped with 15, 20, 25 or 

 30 sets of contacts. The relay occupies a mounting space approxi- 

 mately 2" X 11" and is provided with a cover. 



All contact springs are equipped with twin contacting surfaces 

 similar to the contacts used on the crossbar switch except that they 

 are composed of solid bars of precious metal due to the heavy duty 

 requirements. To facilitate wiring, these relays are manufactured 

 with two types of wiring terminals. In one type the movable springs 

 are of graduated lengths and are provided with notched lugs for bare 

 wire strapping to permit the multipling of springs horizontally to 

 corresponding springs on other relays mounted adjacent. In the 

 second type the strapping lugs are omitted and all springs are of the 



