The following table gives the complete pin assignments for the RS-232 standard. "Cir" is the official RS-232 name for the circuit. "CCITT" gives the CCITT standard number for the circuit. ("Dir." is the direction of the circuit relative to the DCE.)
|
Pin
|
Circuit
|
CCITT
|
Dir
|
Description
|
|
1
|
---
|
---
|
---
|
Shield
|
|
2
|
BA
|
103
|
To
|
Transmitted Data
|
|
3
|
BB
|
104
|
From
|
Received Data
|
|
4
|
CA
|
105
|
To
|
Request to Send
|
|
5
|
CB
|
106
|
From
|
Clear to Send
|
|
6
|
CC
|
107
|
From
|
DCE (Data Set) Ready
|
|
7
|
AB
|
102
|
Both
|
Signal Ground
|
|
8
|
CF
|
109
|
From
|
Recvd Line Signal (Carrier) Detect
|
|
9
|
---
|
---
|
---
|
Reserved for Testing
|
|
10
|
---
|
---
|
---
|
Reserved for Testing
|
|
11
|
---
|
---
|
---
|
Unassigned
|
|
12
|
SCF*
|
122
|
From
|
2nd Carrier Detect
|
|
13
|
SCB
|
121
|
From
|
2nd Clear to Send
|
|
14
|
SBA
|
118
|
To
|
2nd Transmitted Data
|
|
15
|
DB
|
114
|
From
|
Transmitter Timing (DCE)
|
|
16
|
SBB
|
119
|
From
|
2nd Received Data
|
|
17
|
DD
|
115
|
From
|
Receiver Timing (DCE)
|
|
18
|
LL
|
141
|
To
|
Local Loopback Test
|
|
19
|
SCA
|
120
|
To
|
2nd Request to Send
|
|
20
|
CD
|
108.2
|
To
|
DTE Ready
|
|
21
|
RL
|
140
|
To
|
Remote Loopback
|
|
22
|
CE
|
125
|
From
|
Ring Indicator
|
|
23
|
CH*
|
111
|
To
|
Rate Select (DTE Source)
|
|
24
|
DA
|
113
|
To
|
Transmit Timing (DTE)
|
|
25
|
TM
|
142
|
From
|
Test Mode
|
*CI, Rate Select (DCE Source), is assigned to pin 12 only if SCF is not used. Otherwise it is assigned to pin 23.