Appendix B - Cabling, Hardware, & Electrical
302
BLACK BOX
®
Advanced Console Server
Connectors
The connector traditionally used with RS-232 is the 25-pin D-shaped connector (DB-25). Most
analog modems and most older computers and serial equipment use this connector. The RS-
232 interface on DB-25 connector always uses the same standard pin assignment.
The 9-pin D-shaped connector (DB-9) saves some space and is also used for RS-232. Most new
PC COM ports and serial equipment (specially when compact size is important) uses this con-
nector. RS-232 interfaces on DB-9 connectors always use the same standard pin assignment.
The telephone-type modular RJ-45 plug and jack are very compact, inexpensive and compati-
ble with the phone and Ethernet wiring systems present in most buildings and data centers.
Most networking equipment and new servers use RJ-45 connectors for serial communication.
Unfortunately there is no standard RS-232 pin assignment for RJ-45 connectors. Every equip-
ment vendor has its own pin assignment.
Most connectors have two versions. The ones with pins are said to be “male” and the ones
with holes are said to be “female.”
Table 24: Cables and their pin specifications
RS-232 Signal
Name/Function
(Input/Output)
DB-25 pins
(Standard)
DB-9 pins
(Standard)
RJ-45 pins
(Black Box)
Chassis
Safety Ground
1
Shell
Shell
TxD
Transmit Data (O)
2
3
3
RxD
Receive Data (I)
3
2
6
DTR
Data Terminal Ready (O)
20
4
2
DSR
Data Set Ready (I)
6
6
8
DCD
Data Carrier Detect (I)
8
1
7
RTS
Request To Send (O)
4
7
1
CTS
Clear To Send (I)
5
8
5
Gnd
Signal Ground
7
5
4
