Found in old documentation, this circuit uses a double gate MOSFET. The operating frequencies depend on the coil, and the indicator is a microammeter.
This second-order low-pass Salen-Key filter was obtained from an American 1980s documentation. Formulas...
July 2017 - Mouser Electronics is providing the TE Connectivity PTF Series Platinum family RTD...
The basis of this circuit is an LM380 that drives a speaker that emits sound when moisture is...