Abstract

One central unit (NQTC) provided per network section controls a number of remote units (NQTR) distributed over the network section by transmitting to them all data needed for a sequence of test calls via a switched line. The remote units perform the test calls independently based on stored data and store the test results, which results are periodically requested by the central unit. Since a data connection between the central unit and one of the remote units has to be provided only during the data input period; and since the request of results and the remote units work independently during the substantially longer test phase period, there is only a small number of line circuits and modems needed in the central unit; however, a large number of simultaneous test calls can be performed in a network section. The central control can be handled by a processor of small capacity since the processor need not perform any real time work.