All three modem types are identically designed and offer all the advantages of the SIMATIC S7-300 design:

• Compact construction;
  double standard width of SIMATIC S7-300 SM modules
• RJ12 socket for connecting the modem to the WAN (leased line or dialup network)
• 9-pin Sub-D connector with an RS 232 interface for connection to the serial interface of a communication module, e.g. TIM
• 9-pin Sub-D socket with an RS 485 interface for connection to the serial interface of a communication module, e.g. TIM
• 4-pin plug-in terminal strip for connection of the 24 V DC external supply voltage
• Front-panel LEDs indicating TXD, RXD, DTR, RTS/ONL, CTS/RI and DCD
• Simple installation;
  on a mounting rail of the S7-300, or on a 35 mm standard rail
• The SINAUT ST7 modems can be operated without a fan

Configuration examples

An MDx modem is connected to a TIM by means of a standard connecting cable of type 7701. The modem is mounted on a separate S7-300 mounting rail or on a 35 mm standard mounting rail (an appropriate adapter is available).

In the following configuration, the modem is accommodated to the far right in the rack. The TIM is connected to the adjacent module by means of a bus connector. There is no bus connector between TIM and modem. This means that no S7 modules may be used immediately to the right of the modem.

In an S7-400 with TIM 4R-IE the TIM and modem are mounted together on a separate S7-300 mounting rail. The TIM is connected to the CPU by means of one of its Ethernet interfaces. The TIM and MDx modem are connected by means of a standard connecting cable of type 7701.

The following configuration shows the connection of a point-to-point dedicated line network to a TIM 4R-IE, which is used as a control center TIM, for example on the control center PC (e.g. SINAUT ST7cc or ST7sc). Each cable belonging to the point-to-point network is terminated with a modem in the control center. All these modems are connected by means of their RS485 interface to the RS232/RS485 interface of the TIM 4R-IE.