We found this circuit in a Poptronics from 1998. The circuit can be extended to more competitors with another 4011. The power can be made with voltages from 6 to 12 V.
We found this circuit in an ancient American documentation. It can be adapted to operate in other...
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
This circuit reverses the signal if both positive and negative. We found it in an American...