You must have heard this of the parrot –bell and the bird bell. This circuit given here produces a parrot sound repeatedly. A Timmer circuit is also used in the given circuit. This circuit is used to automatically changed the rate at which the parrot sound is repeated. The circuit consumes 15 ma current at a input supply of 6volt. Pin no-2 of the IC 555 is connected to the end- A of the relay. B- end of the of the relay is connected with the ground. The K&L ends of the relay are connected with the winding X-1 of the driver transformer. When the switch S-1 is pressed then the relay is operated for a predetermined time priod. By this the to ends of the driver transformer, which are shorted togther in the normal position of the relay, become open. This result in a changed in the rate at which the parrot sound is repeated. After a delay of about want to 3 seconds the relay comes in the of position and the two ends of the driver transformer get shorted once again. This again result in a chang in the rate at which the parrot sound is repeated this rate can be adjusted by the preset VR-1. value of the capacitor C-3 can also be changed to bring about a chang in the rate of repetition of sound. A real parrot sound is received if the value of this capacitor C-3 is kept 100mf and the value of the resistance connected in series with the speaker is kept at 68E. Effect on the sound should also be observed by using the center tap of the transformer.
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