This small tone generator was found in the November 1987 issue of Radio Electronics magazine. The phototransistor is common and controls the sounds generated. The basic frequency is given by C1.
The modified Hartley oscillator, seen in figure 2, can generate signals ranging from 3 MHz to 10...
This circuit produces a high voltage (above 5,000 V) to ionize the air around a needle that acts...
Found in American documentation from the 90s, this circuit provides three timings given by the...