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.
