Fire detector unit

A fire detector unit comprising:

• a base made of a molded plastic to have a labyrinth wall which projects on the circumference of said base to define therein a smoke chamber, said labyrinth wall permitting an entry of smoke particles but prohibiting the entry of an ambient light into said smoke chamber;
• a light projector carried on said base and directing an incident light from a light emitting element into said smoke chamber;
• a light collector carried on said base and collecting a light scattered by the smoke particles in said smoke chamber to a light receiving element, said light receiving element generating an electric signal indicative of the amount of the light received;
• a fire detecting circuit being connected to receive said electric signal so as to provide a fire warning signal based upon said electric signal;
• and
• a circuit board mounting said light emitting element, said light receiving element, and electronic components forming said fire detecting circuit;
• a metal-made electromagnetic shield which protects said light receiving element from electromagnetic radiation noises;
• wherein
• said electromagnetic shield is integrally molded into said base and has a ground terminal for connection with a ground line of said circuit board,
• said circuit board being fixed to said base by means of metal-made terminal pins which are integrally molded into said base and are electrically connected to said fire detecting circuit, said terminal pins projecting through the circuit board for connection with an external line so as to transmit said fire warning signal.