7d rotary system for small communities
01 July 1932
The paper outlines briefly the main features of the 7D System. The problems to be met were (a) time and zone metering, and (b) numbering. Five different units have been designed: (1) centre exchange, power driven, capacity 200 or 300-5000 lines; (2) sub-centre, power driven, 100-1000 lines; (3) district exchange, power driven, 100-300 lines; (4) district exchange, step-by-step, 50-100 lines; and (5) satellitic exchange, 2 types 10 or 20 lines. The various types are briefly described, and mention is made of the possibilities of remote control routine testing.