Telephone Antiinterference Technique of the German Federal Post Office Telephone System

This paper presents function facilities for suppression of telephone lines and associated subscriber equipment. A setup of test combinations can be arranged by technical clerks at the centralized antiinterference station as well as by a field engineer. The present telephone technique is checked directly from the test desk via direct through-connected lines of the supervisory network. In special cases, remote-controlled measuring equipment and test devices are installed. In the new computerized local electronic telephone exchange system (EWSO 1), remote-controlled test circuits are used primarily, but only by means of trunk circuits of the telephone network. The ac voltages, the frequency of which is analog to the measured value, flow to the test desk via a speech channel and digital information via a data channel. Both facts are visual on the test desks panel The tester can use a service computer via a video data terminal and so be enabled to call from a subscriber index important data for testing a telephone connection. A special test unit can be called from subscriber's plant. This line is then partly checked by automatic steps and partly by dialing of recallable steps. Results are sent to a suppressor as a voicefrequency signal.