Combination: As being the name indicates, this is a smoke detector that makes use of both photoelectric and ionization techniques. The result is an extensive smoke alarm that's not as likely to expertise false triggers. Two- or 4-way circuits hook up initiating gadgets for the fire alarm method’s user interface. https://firealarmsystems03455.life3dblog.com/34286655/not-known-details-about-fire-alarm-systems