Siemens SIMATIC NET TeleControl SINAUT ST7 System Manual page 79

Network structures and topologies
2.2 Configurations
IP-based communication via GPRS with simple security (simple Internet communication)
Figure 2-5 IP-based communication (GPRS/DSL) with MSC protocol via MD720 modem
SINAUT ST7 station control system
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System Manual, 09/2016, C79000-G8976-C178-10