Seven-V narrow pulses from 2 Hz to 50 kHz are produced by this circuit. CI through C4 provide frequency ranges i
n decode steps. Rl and R2 control the charging time of CI through C4. R2 is a potentiometer used to set the frequency. R8 controls pulse width. Pulse width varies from 7 & to 10 ms. Depending on the frequency, R8 can be deleted if it is not needed.