I recently got my hands on a Welch Allyn barcode scanner.  It actually works
(unlike most of the other scanners that I have picked up along the way)

ITEM#	3400LR/C-133

It is a True-RS232 scanner with an extra plug on the cable for power. 
I managed to find a programming manual for the scanner, but it didnt have the
right plugs shown, so here are what I found:

Power Plug.
Female Connector, similar in design to most VGA Card SVHS output connectors,
4 pins with a large lug near the bottom and a small lug at the top.  The top
has an Arrow on it in line with the lug on the plug.

           u
     1   o   o   3
     2  o  D  o  4

u is the small lug right on the top.
D is the large lug near the bottom.
The pin numbers are arbitrary.

Pin 2 is GND
Pin 4 is +5v

To make using integrated parts easier, the GND is wired to RS232 GND pin 5 and
the +5V is wired to the RS232 pin 6.