It is more than that, it is essentially the entire clock containing the primary oscillator and dividers respectively counters. Watch closely, when several digit

It is more than that, it is essentially the entire clock containing the primary oscillator and dividers respectively counters. Watch closely, when several digits change at once, then it emits multiple pulses. Also note that the pulses are emitted from different places, there are essentially three counters, 0 to 12, 0 to 5, and 0 to 9. The three structures above the display are essentially just seven segment decoders, you can see the digit patterns encoded in them similar to mask ROM. There is one column for each digit and two rows for each segment, one to turn the segment on and one to turn it off. If you zoom in on the right of a decoder, the rows are actually labeled with [S]et and [R]eset and a letter A-G for the segment controlled by that row.