This is the circuit diagram of a ding dong sound generator based on two NE555 timer ICs.The circuit is designed to toggle between two adjustable frequencies to produce the ding dong sound. The first NE555 (IC1) is wires as an astable multivibrator operating at 1Hz. The frequency of the second NE555 (IC2) is modulated by the output from the first IC. This is attained by connecting the output of first IC to the control pin (pin5) of the second IC. The tone of the sound depends on the frequency of the second IC and the changeover time depends on the frequency of the first IC.

Circuit diagram.



  • The circuit can be assembled on a Vero board.
  • Use 9V PP3 battery for powering the circuit.
  • POT R4 can be used to adjust the tone of the sound.
  • POT R2 can be used to adjust the change over time.
  • IC1 and IC2 must be mounted on holders.
  • K1 can be a 8 ohms, 1/2 watt tweeter


  1. ahmed nabil

    hey , please i wanted to ask about the capacitors function in this circuit specialy C2 ….. ?

  2. Amit Khobragade


    Is there any replacement for C1 & C4, as I am not able to get those capacitors, the min available are from 25v onwards.

    What will be the diagram changes if I used one of those.?


  3. are c1, c2, c3 are milar capacitors?
    if not, what are its corresponding voltage values? thnx!

    • C1 and C4 are 15V electrolytic capacitors. C2 and C3 are ceramic capacitors.

      • will you please upload some more description about ding dong sound generator using ne 555.???

  4. Is this circuit supposed to make a “higher pitched DING, lower pitched DONG” sound like a doorbell? All I get is “beep beep beep beep beep beep” and I can use the variable resistors to change the length of time of the tones (long beep with a long pause, or very quick), and the other variable resistor to change the tone, higher or lower pitched. But all the tones are the same pitch. Or did I wire it wrong?

    • reply to rendy
      My mistake. I have corrected the circuit diagram.

  5. There should be a 100k resistor between pin 3 IC1 and pin 5 IC2…also you need a button for it to work like a doorbell