1. Resistor
   • R1 (330 ohms, 1/2W)
   • R2 (8.2K, 1/2W)
2. Capacitor
   • C1 (500 uf, 16V)
   • C2 (0.01 uf, 50V)
3. Transistor
   • T1 (BC148B)
   • T2 (AC128)
4. Diode
   • D1 (BY125)
5. Transformer
   • TR1 (230V to 6v step down, 200mA )
6. Miscellaneous
   • Speaker (8 ohms)
   • Neon lamp
   • Pushbutton (S1)
   • PCB or Breadboard
   • Flexible wires

This is a very simple musical electronic bell. In this circuit when the push-button(S1) is pushed, current starts flowing through the transformer. This transformer is a step-down transformer which converts 230V AC to 16V AC. The stepped down voltage is passed through diode D1. Diode D1 behaves as a half wave rectifier and passes only positive voltage. This positive voltage is used to charge capacitor C1. The Charged capacitor C1 acts as a power source for low frequency oscillator. Transistor T1 and T2 are connected in such a way that they constitute a low frequency oscillator of 1 kHz. This oscillating voltage generates oscillating current which flows through the speaker, and generates a sweet tone. The pitch of the generated tone can be changed by using different values of R2 or by using preset of 10K ohms in place of R2.