This circuit was found in a Popular Electronics from the 90s. The circuit uses an ultrasonic microphone. The indicator is dual with LED and Buzzer.
This unit is intended for powering low consumption devices. The operating frequency is...
This high-power amplifier was found in 2001 documentation. The output transistors must be equipped...
July 2016 - It can be obtained from Mouser Electronics new trinkets Adafruit. These trinkets are...