Zipppys123 is building a DIY ultrasonic range finder based on this design. Once it’s externally triggered a PIC12C508 is used to generate generate the ultrasonic pulse, and measure its echo.
The ultrasonic pulse is amplified using a MAX232 TTL-to-RS-232 level converter, while the echo is amplified and demodulated using two op-amps and comparators.
Via the forum.