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 was obtained from an American 80's documentation. The operational ones can be...
This circuit uses two Raytheon RC4558 operational amplifiers that are similar to the 741. The...
This configuration for 3 A currents with a maximum input voltage of 30 V appears elsewhere on this...