This circuit was found in documentation from the 90s. The operational amplifier admits an equivalent. The circuit has frequency ranges up to 5kHz determined by R1.
This triac circuit was taken from an article in the July 1970 Radio Electronics magazine. Note the...
Signals ranging from a few millivolts to a few volts can be used to excite a relay with this...
This circuit was found in American documentation from the 90's. The transformer determines the...