Schematics

Here are the schematics for the PC interface. As you can see, two of the digital outputs from the K8061 are used to control the shift registers, and the remaining 6 outputs each drive 5 8-bit shift registers for a total of 240 digital outputs.
The 8 digital inputs are each connected to 3 8-bit shift register to record a total of 192 inputs. Five analog inputs are used to record the setting of the five potentiometers, and one analog output is used to drive the voltmeter.

The circuits will be realized on 8 pieces of Veroboard (eurocard size): two for the input shift registers, two for the output shift registers, one for the 220 ohm LED series resistors (using resistor packs), and three for the ribbon cable IDC connectors. The 10K pull-up resistors for the switches are placed on the connector boards.