RS-232 Cable Configuration.

CCITT EIA MNEMONIC DESCRIPTION
101 AA GND Protective Ground
103 BA TxD Data Transmitted
104 BB RxD Data Received
105 CA RTS Request to send
106 CB CTS Ready to send
107 CC DSR Data ready
102 AB GND Ground Reference
109 CF DCD Main Detection
108 CD DTR Data Terminal Ready

 

PC MODEM

RS-232  PC to MODEM "DB-25" 25 Pins (DB-25<-->DB-25).

 PC ETD (pin) ECD (pin) modem
GND 1 <---> 1 GND
TxD 2 --> 2 TxD
RxD 3 <-- 3 RxD
RTS 4 --> 4 RTS
CTS 5 <-- 5 CTS
DSR 6 <-- 6 DSR
GND 7 <---> 7 GND
DCD 8 <-- 8 DCD
DTR 20 --> 20 DTR

 

Sandart modem cable RS-232 PC to MODEM "DB-9"  9 Pins (DB-9<-->DB-25).

 PC ETD (pin) ECD (pin) modem
GND 1 <---> 1 GND
TxD 3 --> 2 TxD
RxD 2 <-- 3 RxD
RTS 7 --> 4 RTS
CTS 8 <-- 5 CTS
DSR 6 <-- 6 DSR
GND 5 <---> 7 GND
DCD 1 <-- 8 DCD
DTR 4 --> 20 DTR

 

Modem Macintosh Plus, connector DIN 8 Pins.(Cable Mac<-->Modem DIN-8<-->DB-25)

Name in RS-232 DIN MAC+ Modem Name
DTR HSK0 1 --> 4-20 RTS-DTR
CTS HSK1 2 <-- 5 CTS
TxD TxD- 3 --> 2 TxD
GND GND 4 <----> 7 GND
N.A RxD+ 8 <----> 7 GND
RxD RxD- 5 <-- 3 RxD
N.A TxD+ 6 NC NC NA
NA NA NC NC 1 GND
NA NA NC NC 6 DSR
NA NA NC NC 8 DCD
N.A DEAD 7 NC NC NA

 

Null modem wire

 

DB-25 Pins to DB-25 Pins.(Null Modem DB-25<-->DB-25)

Connector DB-25
(pin)
 
(pin)
Connector DB-25
GND
1
----
1
GND
TxD
2
----
3
RxD
RxD
3
----
2
TxD
RTS
4
----
5
CTS
CTS
5
----
4
RTS
DSR
6
----
20
DTR
DCD
8
----
20
DTR
DTR
20
 
8
DCD
DTR
20
 
6
DSR
GND
7
 
7
GND

 

 DB-9 Pins to DB-25 Pins. Null Modem DB-9<-->DB-25)

Connector DB-9
(pin)
 
(pin)
Connector DB-25
GND
5
----
1 o 7
GND
TxD
3
----
3
RxD
RxD
2
----
2
TxD
RTS
7
----
5
CTS
CTS
8
----
4
RTS
DSR
6
----
20
DTR
DCD
1
----
20
DTR
DTR
4
 
8
DCD
DTR
4
 
6
DSR
GND
5
 
7 o 1
GND