Using a 4046 PLL this circuit recognizes a 1.6 to 1.8 kHz tone by driving an output LED. The circuit is from a Radio Electronics from December 1989.
In the figure we have the circuit of an amplifier for alternating signals with 10 times gain,...
Frequencies up to just over 100 kHz can be obtained with an oscillator based on one of the four...
With this circuit it is possible to regulate a source of up to 9 A using 3 LM350. The integrated...