Musical doorbell (CB9210E)

This musical doorbell was found in a Popular Electronics from the 90s. The U4 melody generator integrated circuit is uncommon today.

| Clique na imagem para ampliar |

Roger Beep (CB16635E)
This circuit for telecommunications was found in a 1987 documentation. Connected to the...
FET photo control (CB8269E)
This circuit is from a 1966 American documentation. The circuit uses a photo-FET, an unusual...
Current Regulator LM217 and LM317 (CB877E)
Currents up to 1.5 A can be regulated with this circuit. The resistor R that determines the...