Counter-dialling

In some cases, it may be helpful to dial oneself out from the target system first, before dialling in to the station from outside. This procedure is known as counter-dialing.

Situations in which counter-dialing is useful:

1. Although the communication parameters have been set up correctly, dialling in from outside by modem cannot take place; the modem cannot establish a connection with the controller.

2. If, for example, the serial cable between the modem and the controller is unplugged and plugged in again during running operation, a connection is not automatically established between the modem and the controller since the interface is, so to speak, still occupied.