This looks like a very modern design inspired by integrated circuits -- the clock is made out of a large number of almost identical sub-circuits. This probably

This looks like a very modern design inspired by integrated circuits -- the clock is made out of a large number of almost identical sub-circuits. This probably makes debugging very easy, but also means that design has much more parts than required. One example is binary to 7 segment decode, which takes entire top of the clock. In this clock, they first fully decode the signal to 10 wires, then amplify it, invert it, and encode it again to 7 segments. That's a lot of diodes, transistor and resistors! We can look at how this was done commercially -- for example in this SN7454 datasheet from 1974, page 6 of http://www.ti.com/lit/ds/sdls111/sdls111.pdf http://www.ti.com/lit/ds/sdls111/sdls111.pdf, they go from 4-bit binary directly into segment driver. This is already fewer parts that this clock has, and in practice, one could reduce the part count even further, for example by grabbing both inverse and direct output of flip-flops. And one can get even smaller if they want to go dynamic indications. Here is a clock with a much smaller part count: http://lovqvist.net/DTL/old%20dtl-clock.html http://lovqvist.net/DTL/old%20dtl-clock.html . Of course, that one would be much harder to debug...