Suggested by General Electric in a 1970 documentation, this circuit makes use of some components of the time, in the case of transistors. The circuit detects smoke by the transparency changing of the air.
This circuit using components that are still common in our market was found in a 1987...
The varactor or varicap diode tunes the signal for listening to SSB signals on a common receiver. The...
This circuit that also serves to control LEDs and other loads is from a 1960 publication. The...