Weird indeed...There's a couple of dip switches as parallel input to the circuit (the 25 pin connector seems to be used as a ground for the switches!) which are then serially shifted into loads of logic gates, flop-flops, inverters etc and the shifted back into an 8 bit parallel output which is fed to the LEDs.

Somehow to me this looks like someone has used this board to prototype some circuit (possible some state machine?) with switches as inputs and LEDs as outputs. But why are there some connections to external connectors on the back? Was the circuit possible simulating some device that would later be connected to serial port / ADB etc? Seems the output also goes through the RS422 line driver to the connector besides the push button. Is this a 8pin serial port?

Would someone be willing to reverse engineering this and build it in Pspice? :lol: