Using LM3909 integrated circuits, this circuit was found in an American documentation from the 90's. The frequencies can be changed by changing the capacitors.
We found this circuit in the Texas Instruments optoelectronics manual. Field effect transistors can be...
Using a CA3059 this circuit was found in the July 1995 Electronics Now magazine. The triac must be...
In this circuit, from a 1977 publication, we have the traditional version of a filter tuned to 1...