We found this circuit in a 1980s documentation. Equivalent components can be used. The circuit senses temperatures in the range of 0 to 50º C and uses a transistor as sensor.
In the figure we have a security system consisting of a sophisticated alarm found in a 90s edition...
This circuit is from an old documentation. However, it can be designed based on modern transistors...
We found this circuit in an 80's Radio Shack publication. The circuit uses a company buzzer, but...