This circuit was found in a 1970's Radio Electronics. The pulse transformer has a 1: 1 turn ratio. The triac must be in accordance with the controlled load.
Today we have more compact solutions. This is from a Radio Electronics magazine from October 1990....
This filter was found in Texas Instruments documentation from the 1980s. The circuit uses a common...
16 commercial test circuit for tubes and transistors appeared in Radio Electronics magazine in...