This sophisticated circuit with two LF411 operational amplifiers appeared in the November 1984 issue of Radio Electronics magazine. The circuit uses a Mallory buzzer as an indicator.
The circuit shown in the figure can be used as an indicator of presence and high voltage in a...
This circuit uses the 2N626, the first commercial Darlington transistor. We found it in Radio...
This circuit can generate signals from 80 to 800 Hz with an amplitude of 0.3 V. We find it in a...