I may help a bit with some very basic stuff, at least enough to get you headed in some directions as to what types of systems are out there.
Once you are briefed to the system types, it's time to do some major web searching, to find additional information.
Additional information is available from the Manufacturers &/or Vendors of the Systems you will be dealing with.
One great resource site for Electronics and anything related is: ePanorama
Check out ePanorama's many areas, and you may find almost everything you need.***Basic Types Of Fire & Security Systems***
Two basic types of Fire Detection / Alarm, and Intrusion Alarm Systems are:
Let's look at the basics of the"Non-Addressable"
These systems normally consist of "Appliances" (detectors, indicators, etc.) and Contacts, which are connected to a "Main Panel", in distinct circuits - referred to as "Zones".
Activation of an alarm status comes from a change of state within a certain zone.
For example, we will use a basic Intrusion Detection System, and describe a single "Loop" which carries appliances and contacts for a single zone.
Let's say the Loop has 2 Passive Infrared Motion Detectors on it, and a single "Door Strike".
("Loop" is the communication, or alarm circuit)
Each Loop is a 2 pair cable - one pair is the comm. circuit's loop, and the other pair is the 24 Volt Power circuit for the Motion Detectors.
The PiR Motion Detectors have both; a set of N.O. contacts, and a set of N.C. contacts.
The N.O. contacts are closed when motion is observed (from received infrared light, produced by a living creature's heat).
The N.C. contacts will open if someone tampers with the device.
The Door Strike will have both N.O. and N.C. as one "switch", which allows the installer 2 options for use; along with a N.C. Tamper Switch for its enclosure.
At the "End" of the loop, we place a Resistor - formally known as the "End Of Loop Resistor" - or simply the "EOLR" or "EOL Resistor" (some refer to it as "End Of Line Resistor").
The value of the EOL Resistor is what will be required to "Load" the Loop up with a steady current value.
This type of System has it's Loops
This Loop will have the following connections:
- Each Motion Detectors' N.O. contacts wired in Parallel across the 2 Wire Comm. Circuit,
- Each Motion Detectors' N.C. Tamper Switch is in Series with the 2 wire Comm. Circuit,
- The Door Strike's N.O. contact is wired in Parallel across the 2 Wire Comm. Circuit,
- The Door Strike's N.C. Tamper Switch is in Series with the 2 wire Comm. Circuit.
During a normal condition - where no motion is detected, and the Door is in its closed position, the Loop draws a "Steady" Current (something like 25 milliamps), and the System observes this as a Normal Condition.
If there is an Intrusion detected - either by one of the motion detectors, or the Door Strike, the effected detector closes the Normally Open contact - which effectively shorts out the EOLR, and causes an increased load current on the Loop.
This is observed as an Alarm State by the Security Panel, and latches in whatever Alarm Annunciation appliances necessary. (sounding off alarm loudspeakers, flashing lights, etc.).
If the Normally Closed Tamper Switch on any device is Opened - due to someone trying to disturb the device, the Loop becomes an Open Circuit - and therefore the "Loading Current" no longer flows as should be.
This is determined to be a fault by the control panel, and initiates a "Trouble" Alarm.
Cutting the Loop's Conductors will also initiate a Trouble condition.
Although this is a VERY SIMPLE DESCRIPTION of a Non-Addressable System, it does convey the basics of its operation.
There are a lot more parameters involved, along with connection schemes and methods of detection.
p.s. Also of interest are the Logic Gates and Op-Amps used for the detection devices, along with inside of the control panels + keypads.
Now a look at the "Addressable"
Found at each Appliance or Contact, is a set of "DIP" Switches. The Switch "Options" are either "0" or "1".
These Switches are used to give each device a unique "Address" on the Communications Loop.
The Comm. Loop (refer to it as the "Comm. Bus") is a 2 Wire Serial Communications Bus, typically done with a shielded twisted pair.
Additionally, a 2 Wire Appliance Power Circuit is run for devices such as Strobes, Horns, Detectors (Heat, Motion, Sound, etc.).
These Circuits are typically made of #14 or #12 THHN Copper Wire.
The Devices in a single Loop may be distinguished from each other, by the ability of "Addressing" each item; therefore, several zones may be monitored using a single 2 Wire Comm. Loop.
If any condition takes place - be it an alarm condition or a trouble condition, the affected device will alert the control panel, and the control panel will display the information received from that certain appliance / switch / device, along with take the necessary actions (like display alarms).
This type of System works like a LAN does - more to the point, it functions similar to larger scale "BAS" (Building Automation Systems) do, with the "LON Topology Concepts".
Be sure to ask me about this, if you need a little more basic information.
As you can see, the Addressable System is much more detailed (and expensive), than it's Non-Addressable counterparts.
The need to be very competent exists on both types of Systems - each one having their own specialty of knowledge base.
Good luck on this Endeavor!
[This message has been edited by Scott35 (edited 07-20-2006).]