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Back-to-Back Connections to a Second Modem
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Back-to-Back Connections to a Second
Modem
Rx Rx
Rx Rx
Tx Tx
Tx Tx
Modem 1 Modem 2
RS-232 (RTU) Interface
Signal
Name
Modem
Input/Output
DB25
Pin
Description
Earth GND
1 Earth Ground
TXD Input 2 Transmit Data
RXD Output 3 Receive Data
RTS Input 4 Request To Send
CTS Output 5 Clear To Send
DSR Output 6 Data Set Ready
(Modem Ready)
SG - 7 Signal Ground
DCD Output 8 Data Carrier Detected
DTR Input 20 Data Terminal Ready
(Host Ready)