Ultrasonic parking system using transistors

A very simple ultrasonic parking system can be designed using this electronic circuit project . This ultrasonic parking system uses few common electronic parts like :transistors, resistors, capacitors and diodes .

As sensors in this electronic circuit project is used two piezoelectric element that must be mounted in “V” like in circuit diagram . When an object is closer to the sensor , a 3kHz sound will be generated in BL speaker . UW1 and UW2 piezoelectric sensors must be mounted at 70cm distance one from another .
This circuit project must be powered from a simple 12 volt DC power supply circuit .