SIEMENS
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Siemens IK PI · 2015
Industrial Remote Communication
Remote Networks
Modems for the conventional telephone network
MD3 telephone modem
7
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Overview
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Dial-up modem for data transfer using the analog telephone
network
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It can also be used as a dedicated line modem.
Duplex data transfer is thus possible in the voice band over
2-wire dedicated lines.
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Private or leased telephone lines can be used as dedicated
lines.
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Benefits
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RS 232 and RS 485 interface
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Isolation between voltage supply and RS 232/RS 485 interface
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Transmission rate on the telephone network and dedicated
line max. 33 600 bit/s
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Application
The MD3 modem can be used as a telephone modem or dedi-
cated-line modem independently of the SINAUT ST7 system.
Due to its design and electrical properties, the MD3 is especially
suited for use in the industrial sector.
Telephone modem
When used as a telephone modem, it enables connections to be
set up with other MD3 or compatible modems, e.g. with the
MD125 and MDM2425B DX modems that were used with the
SINAUT ST1 system.
Dedicated-line modem:
Apart from private dedicated lines, the MD3 can also be con-
nected to Telekom leased lines. Corresponding approval exists.
There are no restrictions in terms of the possible transmission
rates either with exclusively analog leased lines or with analog/
digital converted leased lines.
When used as a dedicated-line modem on private lines, the MD3
enables distances of up to 34 km (at 300 bit/s), 28 km (at 1 200
to 19 200 bit/s) and up to 19 km (at 33 600 bit/s) to be spanned
without amplifiers/repeaters (guide values for uncoiled commu-
nication cable of type 2 x 2 x 0.8 J-Y(St)Y).
When connected to Telekom leased lines, any distance can be
spanned. Depending on the quality of the leased line in each
case, the leased line provider guarantees sufficient reception
signal level at both end points. The line qualities M1020 and
M1025 are recommended.
Used as a dedicated-line modem, the MD3 enables networks to
be constructed in "point-to-point" or "star" configurations. If the
modem is used in the central office, the star network can be ex-
panded to as many as 32 point-to-point connections by linking
several MD3 modems via their RS485 interface.
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Design
The MD3 modem offers all the advantages of the
SIMATIC S7-300 design:
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Compact construction;
double standard width of SIMATIC S7-300 SM modules
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RJ12 socket for connecting the modem via the supplied
connecting cable to the telephone jack or the dedicated line
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9-pin Sub-D connector with an RS 232 interface for connecting
the modem to the RS 232/RS 485 interface of the TIM
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9-pin Sub-D connector with an RS 485 interface for connecting
the modem to the RS 232/RS 485 interface of the TIM
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4-pin plug-in terminal strip for connection of the 24 V DC
external supply voltage
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Front-panel LEDs indicating TXD, RXD, DTR, RTS/ONL,
CTS/RI and DCD
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Easy installation;
the modem is mounted on an S7-300 mounting rail; alterna-
tively, it can be mounted on a 35 mm standard rail using the
adapter 6NH7760-0AA, available separately.
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The modem can be operated without a fan.
© Siemens AG 2014