RS-232 Pin Out - The Definitive Information Sheet

Welcome to this rather boring (but useful!) page which details which wire goes where in an RS-232 connector.

 

Anyone who has worked in comms for a period of time knows the usefulness of the pinout diagram of the RS-232 connector.

So, with our compliments, please find below a diagram showing the relative pin positions and a table detailing the pin assignments

RS-232 Connector Pin-Out Chart
Pin Name To DTE To DCE Function 10 Lines 25 Lines
1 FG     Frame Ground * *
2 TD   > Transmitted Data * *
3 RD <   Received Data * *
4 RTS   > Request to Send * *
5 CTS <   Clear to Send * *
6 DSR <   Data Set Ready * *
7 SG     Signal Ground * *
8 DCD <   Data Carrier Detect * *
9   <   Positive DC Test Voltage   *
10   <   Negative DC Test Voltage   *
11 QM <   Equalizer Mode   *
12 (S)DCD <   Sec. Data Carrier Detect   *
13 (S)CTS <   Sec. Clear to Send   *
14 (S)TD   > Sec. Transmitted Data   *
15 TC <   Negative DC Test Voltage   *
16 (S)RD <   Sec. Received Data   *
17 RC <   Receiver Clock   *
18       Unassigned   *
19 (S)RTS   > Sec. Request to Send   *
20 DTR   > Data Terminal Ready * *
21 SQ <   Signal Quality Detect   *
22 RI <   Ring Indicator * *
23     > Data Ready Selector   *
24 (TC)   > Ext. Transmitter Clock   *
25       Unassigned   *

 

Now, the table is all well and good, however only a few of the pins are used in regular applications.

In fact, very few of the cables purchased these days have more than the essential pins wired.

Please observe the following notes when making your cable:

© Electron Parametrics Ltd 2002.This document may be reproduced in whole or in part provided that this copyright notice is reproduced on each copy made.

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