This double tone generator uses a specific integrated circuit, having been found in a 1977 CMOS Cookbook. The transistors can be the BC548.
This circuit is from 2001 documentation and consists of a small FM transmitter with two inputs, one...
A very interesting and versatile filter circuit, suggested by National Semiconductor is the one...
In this application, from English documentation, we have the way to activate an AC load up to 10 W...