This range meter uses the ultrasonic of about 40 kHz. All of the controls are done by the software of PIC.
http://www.hobby-elec.org/e_psrm.htm
This is a small test program for the Devantech SFR04 Ultrasonic Range Finder, a cheap ultrasonic sensor for robotic applications.
http://members.home.nl/b.vandam/lonely/pagina33.html
Using a modified Devantech SFR04 Ultrasonic Range Finder in an ultrasonic radar application. Displays radar data on a PC with a Visual Basic program.
http://members.home.nl/b.vandam/lonely/pagina40.html
Measure the distance to an object within 25 cm to 8 meters using standard 40 kHz transducers. Takes around 20 samples per second.
http://www.techdesign.be/projects/008/008.htm
http://www.robot-electronics.co.uk/htm/srf1.shtml
http://www.zen22142.zen.co.uk/Circuits/Misc/whistle.htm
http://www.ele.uva.es/~jesus/sonar/sonar.html
PIC16F873 based
http://www.interq.or.jp/japan/se-inoue/e_pic6_6.htm