With this circuit from the September 1989 issue of Radio Electronics magazine, it is possible to receive VLF band signals on a common radio, just like the signals emitted by the previous receiver.
This article was obtained in a French magazine Nouvelle Electronique from 1994. It can be easily...
Suggested by Sprague in the 1980s documentation, this circuit can control three-phase AC motors....
Figure 1 shows a low-pass filter using a 741 operational amplifier but other ICs can be used. The...