Touch sensor (CB8723E)

Found in a 90s Popular Electronics, this circuit uses two PLL tone recognizers to trigger by touch an external load.

| Clique na imagem para ampliar |

Current sensor with 100 M ohm input (CB9663E)
This sensor circuit for currents of the order of nanoamperes was found in an American...
MW Experimental Radio (CB4517E)
This circuit was obtained from a 1964 magazine and has some interesting features such as the input...
Automatic call recorder (CB8656E)
Suggested by a 90’s Radio Electronics, this circuit automatically activates the recording switch of an...