I use a keyboard controller from an old PS/2 keyboard to connect to the PC.
The controller will be connected to an interface I'm still working on, which in turn will be connected to ten pulse generators which will be triggered by the switches.
The buttons will be connected directly to their corresponding pins in the keyboard matrix.
This way, when I flick a switch or press a button, Lock On receives a normal keystroke as if I were using the keyboard :)
Here are some pics showing what I'm working on:
1. Mapping out the keyboard matrix (this has to be done for every type of keyboard we use)
2. Three hours have passed, mapping is finally complete
3. I have connected a floppy cable to the keyboard controller (quite difficult in fact, because the connector pads have a carbon layer over them)
4. Testing the pulse generator. This will give a 0.1 second pulse to the main interface, which will then trigger the keyboard controller
The LED is there to see if it works.
5. PCB design for the pulse generator is complete. I couldn't get it any smaller than this using standard components :)