In this circuit the triac conducts when switch S1 is opened. We found it in the October 1987 Radio Electronics magazine. The triac is controlled according to the load.
This circuit with JFET and Unijunction was found in an ancient American documentation. The...
This metering bridge circuit uses one power supply only. The operational ones depend on the...
We found this configuration in the 1964 RCA transistors manual. As indicator loads in each stage,...