This simple power supply, which is equivalent to 2 AAA or AA batteries, was found in an Elektor from the 90's. The transformer has a 4.5 V secondary with a current of 50 mA or more.
This indicator was found in a 1974 publication, but it can be fitted with the BC548 transistor or...
This circuit has a traditional configuration explored in several other points of this site. The...
This version of a mixer with a transistor appears elsewhere in this section and on this website. The...