This 555-based circuit was found in the August 1976 issue of Radio Electronics magazine. The tone frequencies are provided by the capacitors connected to the 555 IC.
This circuit was found in the February 1981 issue of Radio Electronics magazine. The circuit uses...
Found in American documentation from the 90's, this circuit oscillates up to 150 MHz. The...
This circuit can work with power voltages from 6 to 35 V, being suggested by the Motorola Linear...