This old fashioned transistor amplifier was found in a publication of the year 1958. Transformer are the critical components in the circuit and power comes from 6 D cells.
Found in a 90's EDN, this circuit generates signals in the frequency range given by the graph. The...
The figure shows a circuit that shows how to control an optodiac to trigger a triac from the...
This circuit, from an American documentation from 1975, can be assembled with modern transistors such as...