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Connecting to a Symbol Technologies LaserLink LL-390

I acquired some Symbol barcode scanning hardware at a variety of places, and wanted to know how to hook it up and use it. This was all older gear, and documentation for it wasn't available at the Symbol website. The basic setup is that the scanning device (wand, gun, fixed scanner, whatever) is plugged into an interface device that interprets the data from the scanner and communicates the results to a computer. Symbol has standardized on a DE-9 connector for their scanners, and these can plug into a variety of interface boxes.

The box in question here is an LL-390, which has a single DB-25F connector for data and power. This interface supports both RS-232 functionality as well as the ability to act as an IBM AT-style keyboard wedge. I didn't know the pinout of this connector. My first step was to open the interface and see if I could determine the pinout by examining the PC board inside. I was able to assign functions to some pins (+5V, ground), and signal types to others (RS-232 data in and out), but not actual signals (RXD, DCD, RTS?). The pins were not in the standard locations for RS-232 signals for the most part. A little experimenting revealed that guessing would take a long time, but the board did power up and pass its self test and give the 3-beep "ready" indication when fed 5 volts.

I then went on a hunt for the correct cable, and eventually was able to obtain one, and acquired a second LL-390 in the process. I then proceeded to buzz out the cable, and integrate the findings with my observations of the circuitry to arrive at a reasonably complete understanding of most of the pins and their functions. This information is sufficient to replicate the functionality of the cable, and possibly more. The existing cable sports five connectors, a DB-25M to plug into the LL-390, a DIN-5M and DIN-5F to plug into an AT-style keyboard and CPU, a DB-25F for the RS-232 connection, and an 1/8" mini-phone plug for power. It turns out the device derives the 5 volt supply from the connection to the AT style CPU. I plan to determine whether I can build a variant cable the provides the +5V and +12V from a separate power supply and lets me operate the unit directly from an RS-232 port, as I don't own an AT style PC, and would have to use either a video terminal or USB adaptor with a PS/2 connector, and adapt that to the AT-style DIN-5.

In the meantime, here is the pinout along with the signals, as I currently understand it.

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