Dog whistle circuit ( ultrasonic device )

How to escape from bad dogs :)? You can escape from dogs using a dog whistles sound device with high frequency output because these animals possesses excellent hearing .
With these electronic dog whistles sound circuit described here we can produces an ultrasonic tone which is not audible to humans but which a dog can hear.
The electronic dog whistles from these schematic consists of a piezoelectric speaker (piezotweeter ) which is driven by “bridge circuit “ T1 and T2 on one side and T3 and T4 on the other side which are driven by is the square wave oscillator built around gates IC1.A to IC1.C from 40106 IC.
Because the whistle is not audible to the humans we need to mount Led 1 which will lit when the circuit is active and the whistle circuit is working .
If the whistle circuit is not working , the Led will not flash we need to change the batteries .
To sett the whistle circuit you need to turn the potentiometer P1 until you can not hear the whistle but the dog looks surprised when the circuit is active .
For these whistle circuit we need 9V DC power supply or 9 volts battery .