Found in a Hands-On Electronics from the 90s, this circuit produces the dial tones of an old telephone. The integrated circuit used is uncommon today.
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...