The circuit is from the Linear applications Handbook of the National Semiconductor of 1994. The components used are not common today.
This circuit is from a 1967 publication, but it can be implemented with any Triac of the TIC...
This circuit is from a NEC megaphone made in Japan in the 60s. The circuit has 4 W of power and...
This two-transistor circuit is from a Radio Electronics magazine from April 1965. The transistors are...