Voltage-controlled oscillator (CB20831E)

This circuit is from American documentation from the 90s. The transistor is general-purpose and operational amplifiers can be modern equivalents.

| Clique na imagem para ampliar |

Refrigerator Monitor (CB26012E)
This circuit that detects when the refrigerator is not working properly was found in the February 1997...
Adapter for Multimeter (CB1360E )
If you have a common analog multimeter, you can increase its input resistance in the measurement of...
Car Battery Monitor (CB4542E)
This circuit was obtained from an English magazine from 1980, but as it uses components that can...