This circuit was found in the September 1984 issue of Radio Electronics magazine. The frequency is given by the capacitors. The diodes help in the starting process.
This circuit monitors extra-low frequency (ELF) fields. We found it in an American documentation from the...
We can use any type of resistive transducer with central resistance in the range of 10 k ohms to 1...
This circuit controls two lamps so that when one increases in brightness the other decreases. The...