3571530 is referenced by 12 patents and cites 1 patents.

A remotely controlled telephone loop testing system is disclosed in which the loop test circuits are set up by multifrequency tone bursts from the controlling station. The direct current in the remote loop is transmitted back by being translated into a variable frequency signal which is retranslated to direct current at the control station, and displayed on a meter. All signalling is over nondedicated trunks, and a gate is provided to cut off the variable frequency signal when multifrequency signals are detected on the trunk.

Title
System for remote testing of telephone subscribers lines
Application Number
04/721,907
Publication Number
3571530
Application Date
January 22, 1968
Publication Date
March 16, 1971
Inventor
Davies Chauncey R
Assignee
Bell Telephone Laboratories Incorporated
IPC
H04q 09/12
H04m 03/22
H04M 03/30
H04M 03/28
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