This project presents another application of RF (radio frequency) communication. The capability of fire alarm circuit can be improved by incorporating an RF [[wysiwyg_imageupload::]]module. This way the temperature sensor and buzzer for alarm can be placed away from each other. This provides flexibility in installing various sensors at different locations in a building and thus overheating at a place (due to fire) would signal the buzzer to go on. This project about fire alarm circuit can be divided into four parts, namely, temperature sensor, comparator, transceiver part (RF module) and the output. In this circuit a temperature sensor (LM35) is placed at a certain place and its output is given to the negative end of a comparator. LM324 has been provided in the circuit for comparator. The positive end of comparator is connected to a preset, to set the reference temperature. As long as the output of temperature sensor is below the set reference, the output of comparator stays high.