24-Type testing equipment for telephone subscriber loops

A new transmission measuring system has been developed for the testing of telephone subscriber loops. It consists of an electronically swept oscillator located at the central office and a small measuring set called the “loop checker” used at the subscriber's location. The user sets the loop length information into the loop checker, and with another adjustment the set takes the loop resistance into account. The measurement results in a direct pass-fail judgment of the transmission quality. Companion papers cover the engineering aspects of loop transmission and the results of field tests of the new equipments.1,2