This elementary receiver with a crystal earphone was found in Japanese documentation from the 1960s. The coil has 60 + 40 turns of wire 28 to 32 in a ferrite rod.
We found this circuit in an English magazine from 1976. The magazine no longer exists, but just...
The figure shows a simple way to have emergency power for a 9 V circuit powered by a source. If...
Found in an Electronic Design from the 90's, this circuit supplies voltages according to the...