When someone starts investigating fire protection technology, there are many terms used but very few definitions given for those terms. One such term is analogue smoke detector. To understand what it is, it is necessary to understand the advances leading up to it.
THE STAND ALONE DETECTOR
This is where smoke detection began. Using sensors similar to the more advanced types, what identifies the stand alone detector is the fact that it is not connected to a central system of any type. A self contained unit, such a detector has its own alert built in. Detectors of this type are most commonly found in homes, as they are mandated by law in most places.
THE NON-ADDRESSABLE SYSTEM DETECTOR
This was the next step in fire detection technology. As opposed to a sensor and alert combination, such a detector is simply a sensor that sends a signal to a central computer that makes the "decision" regarding how to deal with the situation. The strength of such a system is that the sensors can be set up in zones. The zones allow responding personnel to quickly find out the general area where the smoke was detected simply by looking at the panel of the central computer. In addition to this, there is far more freedom to customize the alert system with lights and louder sonic alerts. Detectors of this type were used with the first true fire alarm systems and continue to see some use because they are slightly less expensive than options with better features.
THE ADDRESSABLE SYSTEM DETECTOR
While establishing zones was a big step forward in quickly locating and extinguishing a fire, it was usually a somewhat nonspecific indicator, especially in very large systems where a massive number of detectors could be in each zone. The evolution of fire detection advanced to eliminate this issue with addressable detectors. Each detector has an individual address so that when the alarm is tripped, responders can be directed by the central computer directly to the specific detector that signalled the alarm.
THE ANALOGUE DETECTOR
While addressable detectors were close to perfect, a single weakness remained with all fire alarm systems - selectivity of alarm condition. In other words, before analogue detectors, a tiny amount of smoke would trip the entire system. The result of this flaw was false alarms from things as relatively harmless as burned food or cigarette smoke. The analogue detector is an addressable detector that can be tuned to the desired sensitivity. In other words, the system administrator can have the alarm system ignore minor smoke. Analogue Detectors are found in the best systems, where protection is desired without the upheaval of false alarms.