Timing Circuitry
This one is very simple too, pin 11 of U10 receives a signal from the PTT switching Block ( LOW if any VOX is activated ) enabling the counter. Each time any of the VOX is off the counter resets and starts counting again only at the starting of each VOX. U19B is used for setting the maximim continuous on-air togeter with 4 dip-switches. When all inputs of U19B becomes high, the output sets U5A to a logic low and turn the PTTīs off, since all inputs are high during only 1 clock cycle, U5A is used for locking even after this condition has gone. The PTTīs will only ve "unlocked" after U5A gets a logic high from the PTT switchig Block reseting this.
