[Fran] demonstrates the display running with a CD4511B BCD-to-7-segment decoder, hooked up with a bunch of 3904 power transistors to get the chip working with filament bulbs instead of LEDs.

[spencerhamblin] is starting his explorations into digital electronics the hard way: reproducing a “simple” IC’s functionality by wiring up a board full of discrete transistors. In this case ...

The 4511 datasheet specifies that this IC is a BCD to 7-segment latch/decoder/driver with four address inputs (DA to DD), an active. Aspencore network. ... (BI), an active LOW lamp test input (LT), ...