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, which appears at other points on this site, can be designed with both 4011 and 4001...
We found this circuit in an American documentation from the 90s. The circuit applies to vehicles...
Found in Motorola documentation from 1967, this circuit shows how it is possible to obtain a...