/title>sonar navigation for blind this documement is referred to as sonar.htm. the next page is anchored herein as This circuit was designed as an automobile burglar alarm to functon similarly to a heathkit household alarm described in catalogs of the 1970s. But no heathkit circuits or sample was used to design or construct the automotive sample. It was immedeatly observed that the circuits could be used for outdoor navigation by blind people. The circuits per the following sample were mounted in a small box with a 9.0 volt Batterey. Components included two 30KHz pizeoelectric transducers. When turned on in a non-reflective environment, One transducer was in a feedback loop which continuously provided a 30 Khz signal to the near environment. The other transducer provided an attenuated signal to the other transducer and it would lock in to the source. If the system was moved so the transmitted beam was returnd the mixer, an interference signalwas generated that would be detected by the user. This would provide a warning that an obstacle was infront of the user. The was tested in a shirt pocket and would provide a warning signal off a brick wall at 2 meters from the user.Parts for this assembly may be ordered from Digikey corporation 800-344-4539 or any Radio Shack. return to main page <\body> <\html>