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Davies Chauncey R: System for remote testing of telephone subscribers lines. Bell Telephone Laboratories Incorporated, March 16, 1971: US3571530 (12 worldwide citation)

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 ...


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Davies Chauncey R: System for remote testing of telephone subscribers lines. Bell Telephone Laboratories Incorporated, April 27, 1971: US3576450 (1 worldwide citation)

In a system for remote testing of telephone subscribers' lines as disclosed in U.S. Pat. No. 3,410,966, a lockout selector device is provided which selects one control signal at random from a plurality of possible control signals. The lockout selector device locks out all other control signals while ...


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