Standard 1 MHz Oscillator (CB9653E)

We found this circuit in an old American documentation. Transistors can be modern equivalents.

Automatic Night Light (CB10690E)
This circuit was published in an English magazine from 1972, but it can be easily implemented...
DVM to PC adapter (CB7924E)
This circuit from a Popular Electronics from the 90s allows you to use an old PC as a digital...
Tone Activated Relay (CB13696E)
With the values of the components of this circuit, tone recognition can be done in the range of...