Simple Telephone Ring Tone Generator Circuit

This is the figure simple telephone ring tone generator circuit designed using only a few components. It produces simulated telephone ring tone and needs only DC voltage (4.5V DC to 12V DC). One may use this circuit in ordinary intercom or phone-type intercom. This is the figure of the circuit;

The sound is quite loud when this circuit is operated on +12V DC power supply. However, the volume of ring sound is adjustable. The commonly available 14-stage binary ripple counter with built-in oscillator (CMOS IC CD4060B) is used to generate three types of pulses, which are available from pin 1 (O11), pin 3 (O13), and pin 14 (O7), respectively. Preset VR1 is adjusted to obtain 0.3125Hz pulses (1.6- second ‘low’ followed by 1.6-second ‘high’) at pin 3 of IC1. At the same time, pulses available from pin 1 will be of 1.25 Hz (0.4-second ‘low’, 0.4-second ‘high’) and 20 Hz at pin 14. The three output pins of IC1 are connected to base terminals of transistors T1, T2, and T3 through resistors R1, R2, and R3, respectively.