Originally Posted by
angelw
Hi Dave,
Pin 25 on a DB25 connector is used for no purpose other than testing. Accordingly, its probably safe simply because its highly unlikely that any connection to it would be made. The voltage for the RS232 control circuit is +3v to +25v for logic 1, notwithstanding that its generally around 9v to 13v, and although I've not done so, it should be safe to connect the control lines to pin 25 (but I'm not sure what protection this pin has), if for some reason pin 20 was not viable. Further, it should be safe to connect an external devices that uses RS232 protocal to it.
I've never heard of any equipement being damaged because of the voltage from pin 25, but it would be possible if the device couldn't tolerate that voltage level and there was a short to it, but no more so than being damaged by the voltage from pin 20, although, as stated before, pin 20's voltage is normally around 9v to 13v.
Regards,
Bill