Siemens SIMATIC S7 Operating Instructions Manual page 64

SIEMENS AG PRODAVE S7
A modem connection is basically only estalblished with the TeleService functions.
There are two possibilities in order to establish the connections
o actively by the PG/PC using the ts_dial function
When access protection is activated the TS-Adaptor checks the specified password.
Providing the password is correct, the connection is established either immediately or
after re-dialling from the TeleService Adaptor (depending on TeleService
parameterisation).
The function ts_dial returns the connection status and / or in the event of an
asynchronous call of function ts_dial the message TS_CONNECTED (connection
established) or TS_DISCONNECTED (connection not established) is sent to the
specified window only after the connection is established or if the TeleService
Adaptor replies with error (e.g. password not correct).
Toolbox for Data Link PGs/PCs to SIMATIC S7
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