This receiver was found in a Popular Electronics from the 90's. Its different configuration shows a tuning circuit after the tube that works as an aperiodic amplifier. Observe supply voltages.
We found this different configuration that uses a fluorescent lamp as a negative resistance device...
The integrated circuits used in this thermometer are not very common today. The indicator is a...
In the figure we have the way to control a triac of the TIC series with a low voltage through a...