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 was suggested by National Semiconductor in its 1994 Linear...
In the figure the well-known basic configuration of relaxation oscillator with unijunction...
This 2 meter (144 MHz) preamplifier is intended for use with portable transceivers. The...