This 1968 Texas Instruments circuit uses diacs of the era. SCRs can be modern equivalents according to the controlled load.
The gain of the operational amplifier shown in the figure depends on the feedback resistor,...
This circuit is from a 1970 publication. The time constant is given by 1.3R x C where R is the...
This commercial medium and short-wave radio was manufactured in Japan in the 60s. The circuit has...