Building a simple circuit with 39 transistors, 31 resistors, and a handful of diodes is a good introduction to digital electronics, and after two attempts, [spencerhamblin] knocked it out of the park.

By combining 49 of them he’s put together a soda bicarb diode steering circuit for a 7-segment display capable of showing the digits 0 to 9. He takes the idea for his diode from electrolytic ...

Another one is the TTL IC 74LS47 which is a BCD decoder/driver for seven segment common anode (CA) displays. Note that, the IC 74LS48 also makes the same work, but designed for seven segment common ...