Found in a Hands-On Electronics from the 90s, this circuit produces the dial tones of an old telephone. The integrated circuit used is uncommon today.
This sensor circuit for currents of the order of nanoamperes was found in an American...
This circuit was obtained from a 1964 magazine and has some interesting features such as the input...
Suggested by a 90’s Radio Electronics, this circuit automatically activates the recording switch of an...