58kohm resistors represent nixie tube digit elements. 10kohm resistor is anode resistor.
All digital inputs are active low.
Upper inputs select which tube is active. Lower inputs select which digit is active on the tube. (Only 2 tubes with 4 digits each are shown.)
For a clock with 6 digits, a total of 16 n-channel FETs and 6 p-channel FETs are required. Diodes prevent reverse current through inactive tubes.
Logic inputs can be driven with BCD-to-DEC decoder similar to SN74LS145N to reduce required pins on microcontroller.
