Overview
© Siemens AG 2002 All Rights Reserved 6NH7811-0AA22
MD2 Modem (07/2002) 1-3
1.2 Main Features
The MD2 modem has the following features:
• SIMATIC S7-300 design (see Fig. 1-1)
• Can be mounted on a S7-300 mounting rail or a 35 mm standard rail
(using the optional adapter 6NH7760-0AA)
• 24 V DC power supply connection, power consumption 100 mA
• RS232 port (9-pin sub-D plug) and RS485 port (9-pin sub-D socket)
• Potential insulation between power supply and RS232/RS485 interface
• Choice of 4 different transmission speeds: 1200, 2400, 9600 or 19200 bps
• It is possible to use baud rates lower than 1200 bps in several operating modes
(compared to 1200 bps no range extension can be achieved with lower baud
rates)
• Choice of 4-wire full-duplex or 2-wire half-duplex transmission mode
• Integrated double transformer for two 2-wire lines
• Send level can be switched from -6 to 0 dB
• Tapping capable
• Parallel connection of several MD2s to one data terminal (DTE, data terminal
equipment), for example to connect a star network
• Integrated repeater function (by connecting two MD2s) for range multiplication
• Conversion from 2-wire to 4-wire or from 4-wire to 2-wire is possible in repeater
mode
• Switched optocoupler output with RTS signal for switching connected radio
equipment on and off
• RS485 interface for 2-wire half-duplex with automatic direction recognition
• Automatic refresh of received data before transfer to the DTE
• Certified for telecom leased lines using 1200 and 2400 bps. This only applies to
purely analog telecom leased lines. For telecom leased lines using
analog/digital conversion, only 1200 bps can be used (see section 1.5)
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