Suggested by a Philips documentation from 1970, this circuit uses period components, operating at 50 Hz. The current consumed is 10 A and the input voltage is 12 V.
This simple metal detector was found in a 1960 Sylvania transistor manual. The phone must be high...
This is one of the many versions of this type of indicator that the reader can find on our...
Found in an English publication from the 1980s, this circuit can be built with equivalent...