Telephone Busy Indicator (CB24430E)

This circuit for analog telephones from the 90s was found in documentation from the time. It lights up a remote LED when the extension is in use.

| Clique na imagem para ampliar |

5 V Power Supply (CB25403E)
This battery-powered micropower supply was shown in Radio Electronics magazine in 1991. The...
Basic timer (CB21427E)
Found in a 1965 Electronic Design, this circuit can be made with modern equivalent transistors. The...
Circuit for Determining the Force of a Solenoid (CB11879E)
In this circuit, the current in solenoid X1 can be adjusted and its intensity measured to the...