Connection of data link between PABX and main exchange - using modem automatically connected by dialling correct number

摘要

The principle application of the data link is to enable a main telephone exchange to check the functioning, alter functions, or receive information from, a p.a.b.x. In the p.b.x. installation (NST) an internal line is connected through a special subscriber unit (TSP) to the number selection network. This unit has a change over-switch (U) to select a modem (MP) instead of a handset (T). When the main exchange (VZ) dials the appropriate code number the receiving and processing equipment (AUe,WAS, ZST) in the branch selects the dedicated extension, and switches over the call to the modem. The central exchange is then in direct contact with the branch processor (ZST), and can carry out the required data exchange. The equipment can also be adapted to set up a data link with another subscriber by direct dialling via the public telephone network.