T 4.25 Still active connections

An ISDN communications adapter might actually fail to close down a connection established previously via the communications software. If such a defect is suspected, it can be verified easily by calling the corresponding ISDN subscriber number.

Example:

Before leaving on a 2-week vacation, a network administrator established an ISDN data connection with his Internet provider. On completion of the session, the ISDN connection was not terminated properly. On returning from his vacation, the network administrator was surprised to see the large bill he had received for ISDN services