3705275 is referenced by 5 patents and cites 1 patents.

A system for testing telephone trunks, particularly trunks in tandem extending between three or more crossbar offices, in which each trunk circuit is given a line location and a local telephone number in its own office. The switching equipment in each office is arranged so that when it receives a trunk circuit telephone number from a test board, it establishes a connection directly to that trunk circuit, as if it were a line circuit. Thus, the test board in one office can select a trunk to a second office, thereby seizing a register-sender in the second office; it can then dial into that register-sender the telephone number of a desired trunk from the second office to a third office, thus seizing a register-sender in the third office, and it can then dial into such register-sender the telephone number of test equipment in the third office, allowing the trunks to be tested in tandem.

Title
Telephone trunk testing system
Application Number
05/185,185
Publication Number
3705275
Application Date
September 30, 1971
Publication Date
December 5, 1972
Inventor
Davey Murray Allan
Leyburn Derek
Assignee
The Bell Telephone Company of Canada
IPC
H04b 03/46
H04M 03/28
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