For instance, here's one that I just happen to have to hand. The Rigel 277 Safety Tester, which uses the standard 9-pin D-shell connector:-
Pin 1 - Not connected
Pin 2 - Rx
Pin 3 - Tx
Pin 4 - DTR
Pin 5 - Zero volts
Pin 6 - Not connected
Pin 7 - Zero volts
Pin 8 - Not connected
Pin 9 - +5 volts
Baud rate : 9600
Data bits : 8
Start bits : 1
Stop bits : 2
Parity : none
Rx : Received Data
Tx : Transmitted Data
DTR : DTE Ready
DTE : Data Terminal Equipment ... almost always a PC or similar
DCE : Data Communications Equipment (but originally Data Circuit-terminating Equipment per RS-232 ... and back then, almost always a modem)
For comparison, here are the "offical" 9-pin RS-232 pin-outs:-
Pin 1 - Received Line Signal Detect
Pin 2 - Received Data
Pin 3 - Transmitted Data
Pin 4 - DTE Ready
Pin 5 - Signal Ground
Pin 6 - DCE Ready
Pin 7 - Request to Send
Pin 8 - Clear to Send
Pin 9 - Ring Indicator
... so in this case, the Rigel 277 connections are a near approximation, which is all nice and proper!
See
here for some nice information about RS-232 connections. There's even a
forum, for those who are really keen.
