This biestable vox circuit was found in an old documentation. The circuit makes use of components of the time (80's) and can work as a shield since the power is 5 V.
This circuit was found in a Popular Electronics from the 90s. Transistors are general purpose...
This circuit works with only 1.5 V and can be powered by a solar panel. The circuit is from 1991....
This circuit has a maximum output current of 5 A, and the 2N3055 must have an excellent heat sink....