This circuit was found in a Motorola manual from 1968. As it can be obtained 20 V at 15 kHz from 120 V x 60 Hz. The components are of the time.
This circuit was published in an English magazine from 1980. The magazine no longer exists, but...
We found this circuit in an old American documentation, from 1971, but the component used is still...
This circuit is from a 1991 publication, but it can be assembled with more modern components. We...