We found this parallel regulator in a 1973 publication. Transistors admit equivalents and the output voltage can be modified by changing the zener.
This is a Japanese commercial radio from the 60s. The circuit is listened to by phone and is...
The first circuit we present is ideal for matching the low impedance of transducers, such as...
We found this circuit in Motorola's Linear Databook in 1990. The component used is not common today....