Ring tones in the old telephone sets and piezo buzzer in the current electronic telephone instruments are not so melodious. In order to make telephone ringtones soothing and pleasant to the ears. Here is a simple circuit that generates musical tones when there is an incoming call. The circuit can be used for many purposes like intercom bell, calling bell, etc. It is based on two 555 timer ICs that are connected together to act as an astable multivibrator.
A multivibrator is a positive feedback regenerative switching circuit with analog timing of switching behavior. The astable multivibrator has actually no stable state. It has two quasi-stable states which rapidly alter from one to another and again to the same state. So it mainly alters from high to low and from low to high irrespective of any input trigger input after a pre-settled time.
Hardware Components
The following components are required to make Telephone Ringtone Generator Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | IC | NE555 Timer | 2 |
| 2. | Variable resistor | 10K, 100K | 1 |
| 3. | Speaker | 8 ohm | 1 |
| 4. | Electrolytic Capacitor | 10uF | 1 |
| 5. | Ceramic Capacitor | 10nF | 1 |
| 6. | Resistors | 50K, 10K, 1K | 1, 3, 1 |
| 7. | Battery | 6V to 12V | 1, 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Telephone Ringtone Generator Circuit
Working Explanation
This circuit is capable of generating quite a loud ringtone when operated with a 9-12V DC supply. The two 555 timer ICs are connected as an astable multivibrator such that the output of IC1 Is fed to the pin5 of the IC2 through a 10K variable resistor. They are connected in such a manner that the output frequency of IC2 is controlled by IC1. The output sound is adjusted 8ohms (0.5W-1W) speaker is used at the output of IC2 connected through a 10µF capacitor to give a melodious ringtone.
Applications and Uses:
This circuit that generates pleasing and melodious musical tones when there is an incoming telephone call. The circuit can be used for many purposes like intercom bell, calling bell, doorbell, etc.
