D-Sub Pinouts (RS-449, RS-232)

D-sub connectors. also known as "DB connectors" are electrical connectors that contain two or more parallel rows of pins or sockets.  The pins are surrounded by a metal shield that is shorter on one side, resembling the letter D. They come in 9, 15, 25, 37, and 50 pin varieties. 

Some may not follow the standard pinout listed below. Please refer to documentation for specific pinouts. Failure to do so may result in damage to your equipment. Clark Wire and Cable does not accept responsibility, or liability for any loss, damage, cost, or expense that you may incur as a result of the information provided below.

DB-37 Pinout (RS-449)

RS-449 is a serial communications standard that defines the interface between data terminal equipment (DTE) and data communications equipment (DCE). The standard is also known as EIA-449 or TIA-449.
* Rear view of male 37 pin D-Sub connector

(BOTTOM ROW) (TOP ROW)
37 send common 19 signal ground
36 standby / indicator 18 test mode
35 terminal timing (B) 17 terminal timing (A)
34 new signal 16 select frequency
33 singal quality 15 incomming call
32 select standby 14 remote loopback
31 receiver ready (B) 13 receiver ready (A)
30 terminal ready (B) 12 terminal ready (A)
29 data mode (B) 11 data mode (A)
28 terminal in service 10 local loopback
27 clear to send (B) 09 clear to send (A)
26 receive timing (B) 08 receive timing (A)
25 request to send (B) 07 request to send (A)
24 receive data (B) 06 receive data (A)
23 send timing (B) 05 receive timing (A)
22 send data (B) 04 send data (A)
21 03
20 receive common 02 signal rate indicator
01 signal ground
  • Rear view of female 37 pin D-Sub connector

DB-25 Pinout (RS-232)

RS-232 defines three types of connections: electrical, functional, and mechanical. The most commonly used interface, RS-232 is ideal for the data transmission range of 0-20Kbps/50 ft. It employs unbalanced signaling and is usually used with 25 pin D-type connectors (DB25) to interconnect DTEs (computers, controllers, etc.) and DCEs (modems, converters, etc.).
  • Rear view of male 25 pin D-Sub connector

(BOTTOM ROW) (TOP ROW)
25 (no connection) 13 secondary clear to send
24 DTE transmitter signal element 12 secondary received line 
23 data signal rate selector 11 (no connection)
22 ring indicator 10 negative voltage
21 signal quality connector 09 positive voltage
20 data terminal ready 08 received line signal detector
19 secondary request to send 07 singal ground / common return
18 (no connection) 06 data-set-ready
17 receiver signal element timing 05 clear to send
16 secondary received data 04 request to send
15 DTE transmitter signal element timing 03 received data
14 secondary transmitted 02 transmitted data
01 protective ground
  • Rear view of female 25 pin D-Sub connector