The left 4 (horizontal) switches are the inputs (from 0(000) to 16(1111)).
BCD value are from 0 to 9, 0 to 1001. If the value is above 9, the top lamp will stay ON.
The switch on the data path is the Enable switch.
Each relay should come with a protection diode.
The goal of this circuit is to drive a diode based memory array of size 10 lines by 7. Each line will drive a 7 digits display. The last line will drive the 0/1 second display.
