RS232 standards
EIA RS232-C (CCITT V24)
Notes
Transmission is serial (asynchronous).
MARK = binary 1 = OFF = -3 to -25 volts.
SPACE = binary 0 = ON = +3 to +25 volts.
25-pin "D" type connector.
Data Control Equipment (DCE) has -female connector.
Data Terminal Equipment (DTE) has male connector.
Open circuit drive voltage cannot exceed 25 volts.
Terminator resistance 3-7K ohms.
50 -foot maximum DCE, DTE separation.
2500 pico farad max conductor capacitance.
CIRCUIT
PIN
NAME DIRECTION
CCITT EIA
FUNCTION
01
FG
-
101
AA
Frame Ground.
02 TD To DCE 103 BA Transmitted Data.
03 RD
To DTE 104 BB Received Data.
04
RTS
To DCE 105
CA Request To Send.
05 CTS
To DTE
106 CB Clear To Send.
06 DSR
To DTE 107 CC Data Set Ready.
07
SG
-
102 AB Signal Ground.
08
DCD
To DTE 109
CF
Data Carrier Detect.
09
To DTE
Positive DC Test Voltage.
10
To DTE Negative DC Test Voltage.
11 QM
To DTE Bel 1 208A Equaliser Mode.
12
(S)DCD To DTE 122 SCF
Secondary Data Carrier Detect
13 (S)CTS To DTE
121 SCB
Secondary Clear To Send.
14
(S) TD
To DCE 118 SBA
Secondary Transmitted Data.
NS To DCE Bell 208A
New Synch.
15 TC
To DTE 114 DB
Transmitter Clock.
16
(S)RD
To DTE
119 SBB
Secondary Received Data.
DCT To DTE Bell 208A
Divided Clock Transmitter.
17
RC To DTE
115
DD Receiver Clock.
18 DCR To DTE Bell 208A
Divided Clock Receiver.
19
(S)RTS
To DCE
120
SCA
Secondary Request to Send.
20 DTR To DCE 108.
2 CD
Data Terminal Ready.
21
SQ To DTE 110 CG
Signal Quality Detect.
22
RI
To DTE 125 CE
Ring Indicator.
23 To DCE
111
CH Data Rate Selector.
To DTE 112
Cl
Data Rate Selector.
24
TC
To DCE
113 DA
EXT Transmitter Clock.
25 To DCE
Bell 113B
Busy.
79
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