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6.2.5
RS232 Interface (EIA574)
The RB900 terminal is equipped with an RS232 interface (as shown below). The DE9
DSUB socket is connected via a voltage level translator circuit to the GSM module.
Table of RS232 DB9 pins:
Pin No.
Name
1
DCD
2
RD
3
TD
4
DTR
5
SGND
6
DSR
7
RTS
8
CTS
9
RI
13
Dir
IN
Data Carrier Detect. Raised by DCE when modem
IN
Receive Data (a.k.a RxD, Rx). Arriving data from DCE.
OUT
Transmit Data (a.k.a TxD, Tx). Sending data from DTE.
OUT
Data Terminal Ready. Raised by DTE when powered on. In
auto-answer mode raised only when RI arrives from DCE.
-
IN
Data Set Ready. Raised by DCE to indicate ready.
OUT
Request To Send. Raised by DTE when it wishes to send.
IN
Clear To Send. Raised by DCE in response to RTS from DTE.
IN
Ring Indicator. Set when incoming ring detected - used for auto-
answer application. DTE raised DTR to answer.
DE-9 (EIA/TIA 574)
looking into female connector
Description
synchronized.
Ground
Expects CTS from DCE.
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