Is there anyone who can give any possible explanaiton?

[drinalds]

**broken link removed**

this kind of circuit is jogging timer....i need only is the circuit operation
plss click to see full detail.... https://www.redcircuits.com/Page32.htm

 

[hyedenny]

Hi,
Your circuit works like this: R2, R3, and C2 generate the clock signal and determine the speed at which IC2 counts. The values for R3 and C2 are determined by T=2.2xRC. Output Qn is the nth stage of the counter IC2. In this case, the output of pin 14 represents the division of the count of the oscillator by 256. Every time output pin 14 of IC2 goes high, it sends a signal to IC3 input pin 14 - its clock pin. This changes the output of IC3 by one successive count. Selecting the DIP switch enables only that decoded count to be selected. The Schmitt triggers invert and buffer that signal which drives the NPN transistor, Q1, to saturation, which allows current to flow through the buzzer.