3822367 is referenced by 5 patents and cites 6 patents.

A method and apparatus for testing a plurality of private information transmission lines which connect a plurality of regional offices with a plurality of local offices from a single location at a home office. A commercial telephone circuit link is established between the home office and the regional office associated with the transmission line to be tested by dialing the telephone number of the regional station at the home station on a commercial telephone handset. A selective coupling means is provided at each regional office for selectively coupling the information transmission lines at that office with the commercial telephone lines at the office and hence providing a complete testing loop from the home office to the transmission lines and back to the home office. The coupling means includes means for matching the impedance of the commercial telephone lines and the private transmission lines, means for adjusting the levels of the signals entering and exiting from the regional office and means for selectively connecting any of a plurality of transmission lines to the commercial telephone lines.

Method and apparatus for remote testing of a transmission line
Application Number
Publication Number
Application Date
August 29, 1972
Publication Date
July 2, 1974
Humphrey Marion L
Browne Beveridge DeGrandi & Kline
Allstate Insurance Company
H04b 03/46
H04M 03/32
H04M 03/28
H04B 03/46
View Original Source