Figure 5. Counter outputs and Carry Out signals.
The sync pulse at pin 15 U4 occurs when the Carry Out (pin 12) of U5 goes from low to
high. At that time, C6 and R16 generate a positive pulse of about 1us to reset U4 to
zero count so that U4 and U5 will synchronize their counting. The pulse occurs once
every ten clock cycles. The waveform is shown in Figure 6.The pulse is very narrow
(about 1us) compared to the clock cycle (about 10ms). Use the highest clock frequency
by dialing VR1 to the lowest resistance.
