All the information relevant to setting up a teleservice connection between an S7-200 controller and MD 720-3 as Remote Station of a local station based on the Micro Automation Sets 21 (Entry ID: 22537809) is available in the document provided here.
Attachment 1: Teleservice_MD720-3_v1d1_en.pdf ( 1152 KB )
The SINAUT MD720-3 modem supports both GSM and GPRS communication. For GPRS communication, however, you also need the SINAUT MICRO SC software for the OPC server. For the use of teleservice only, you can also use the GSM modem SIPLUS TC65T (Entry ID: 26955813)
Teleservice, GSM, S7-200 CPU, Controller, MC45, Terminal, Remote connection, Communication, Service, CSD, STEP 7 Micro/WIN