Found in an old English publication, this circuit applies to the 240 V network, but can be changed to lower voltages. Transistors are mostly general-purpose, admitting modern equivalents.
This circuit was found in Radio Electronics from the 90s. The transistor is for general use. The...
We found this circuit in a 2005 Linear Technology application manual. The circuit makes use of a...
This circuit is from 1971 American documentation. Transistors are still common except for 2N2060...