method for controlling the functional ability of sections of lines and stations, for accessibility of emergency calls

摘要

A method of checking the operability of line sections and the permanent availability of an emergency enquiry station NRA in which there are assigned to each of the emergency enquiry stations NRA special signal sources SA, each for generating a test signal which also conveys an indication of its own station, which periodically occupy the groups of lines between the switching centres VST associated with the stations NRA with checking operations. in a called emergency enquiry station NRA, an indicator effects the identification of the state of a line. Change-over of a local network area to guarantee availability is always initiated by the taking-over emergency enquiry station NRA, and permanently connected lines LT are provided between the switching centres VST for this purpose. IMAGE