This circuit triggers a relay when the set temperature is reached. The circuit is from an old documentation. The relay may be equivalent according to the transformer secondary voltage.
This 1995 circuit uses an audio amplifier that is no longer common today. However, other...
The tone produced by this circuit attract fishes. The circuit is installed into a small can and...
This circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply...