low cost fire alarm circuit

This document describes a low cost fire alarm circuit project. It includes an introduction to fire alarms and their importance. The circuit uses transistors as heat sensors to detect a fire and trigger a relay connected to alarms. When the temperature rises, the leakage current of one transistor increases, biasing a second one on and activating the relay. The circuit provides fire detection at low cost with simple components and circuitry. It has advantages of low price, ease of use and portability but cannot detect extremely high temperatures. The summary aims to capture the key purpose, components, working and benefits of the circuit in 3 sentences or less.