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Last updated: November 26, 1999


RS-232 Signals

PIN SIGNAL SIGNAL NAME FLOW DESCRIPTION
2
14
BA
or
TD
Transmit Data Output Data transmitted to the data communications equipment.
3
16
BB
or
RD
Receive Data Input Data received from the data communications equipment.
4
19
CA
or
RTS
Request to Send Output Signal sent to the data communications equipment, asking if it is ready to start accepting data.
5
13
CB
or
CTS
Clear to Send Input Ready to accept data signal from the data communications equipment.
6 CC
or
DSR
Data Set Ready Input Data communications equipment indicates the status of the local data set.
7 AB
or
SG
Signal Ground None Signal Ground provides a reference level for the signal voltages.
8
12
CF
or
DCD
Data Carrier Detect Input Data communications equipment detected "carrier." Example: a modem senses tones sent to it by another modem over phone lines.
15 DB
or
TC
Transmit Clock
from DCE
Input Transmit clock from the modem. Usually not used for asynchronous devices (terminals, printers, and modems, etc.).
17 DD
or
RC
Receive Clock
from DCE
Input Receive clock from the modem. Usually not used for asynchronous devices (terminals, printers, and modems, etc.).
20 CD
or
DTR
Data Terminal
Ready
Output The DTE is powered on and ready to communicate as the "local data terminal" with the data communication equipment. For example, the modem.
24 DA
or
TCO
Transmit Clock
from DTE
Output Provides transmit clock from the DTE. Usually not used for asynchronous devices (terminals, printers, and modems, etc.).


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