This pulse generator can provide up to 12 pulses at its output depending on the setting of hexadecimal switches S2 – S3.
The (rectangular) pulses are generated by IC3c with circuit values as shown their p.r.r (pulse repetition rate) is a few KHz.
The output of generator is taken to one input of NOR gate IC2c vai buffer inverter IC3b
When switch S1 is operated bistable IC1a receives a clock pulse, whereupon logic 1 is passed to the D input (pin 12) of IC1b via IC2a. The other input of IC2a is low because counter IC3 is disabled via its reset input. At the next leading clock edge, the bistable is set, so that IC3 and via IC2b the pulse output are enabled.
When the relevant number of pulses has been output junction R3 – S2 goes high whereupon the output of IC2a goes low and IC1b passes a logic 0 from its D input to pin 9.
IC1a is reset via C1 so that S1 can be operated again and the counter is reset via pin 8 of IC1b. Also, pin 8 disables gate IC2b, so that no more pulses can appear at the output.
The generator draws a current of only 2.5mA.