Abstract: ISDN telecommunications network and method for the monitoring and checking of subscriber connections of the ISDN telecommunications network. The telecommunications network includes a plurality of subscriber connections, and at least one checking station that is connectable to a desired one of the plurality of subscriber connections. Each of the plurality of subscriber connections includes an answering station adapted to receive messages from and send messages to the checking station. The at least one checking station includes a device to establish a connection with the desired one of the plurality of subscriber connections, and the answering station is adapted to be placed into a monitoring state. Signaling information exchanged over the D channel associated with the desired one of the plurality of subscriber connections is transmitted to the checking station.