Communication between the control panel and its intelligent and addressable devices takes place along a Signaling Line Circuit (SLC) . This interface integrates a fire alarm control panel with several types of devices, each with a specific function to perform. Below is the variety of devices that are tipically employed in a SLC:
Intelligent Detectors to identify a variety of threat conditions like various smoke levels, heat, CO, etc.
Addressable Modules to interface the system to convenctional input/output circuit and devices – notificaction appliances, smoke detectors, waterflow and supervisory devices, etc.
Addressable Pull Stations for manual fire alarm activation.
Loop fault Isolators to prevent total loop failure from an SLC short.
FlashScan is a communication protocol that greatly enhances the speed of communication between an intelligent control panel and its SLC devices. If one of the devices in the group has new information, the panel CPU´s stops the group poll and concentrates on single device. By polling modules in groups of 10, the net effect is a response speed much greater than that of earlier protocols.
FlashScan protocols also permits the largest number of devices per loop in the industry (159 detectors/159 modules).
Every device on a perticular Signaling Line Circuit must be FlashScan compatible for the protocol to function. If a single CLIP device is installed on the circuit, the panel will revert its communication protocol to CLIP.
The SLC is a power limited circuit but is not supervised in the same sense as a convenctional circuit. Supervision is accomplished by actually “talking” with each device, not by passing current around a circuit through an End-Of-Line Resistor.
Notifier offers two devices that can be used to protect critical elements of the FlashScan – mode or CLIP-mode SLC Loops from faults on other SLC branches or segments:
ISO-X : Fault Isolator Module
B224BI : Isolator Detector Base
These devices funtion really like a Ground Fault Interrumper (GFI) on a common household electrical circuit, with the difference that the short is across the positive and negative legs of the SLC Loop, not to ground.
The ISO-X continuously monitor the circuit connected to terminals 3(-) and 4(+). If the module detects the short, it opens the faulted branch, preventing it from affecting the communications of the reminder of the SLC Loop.
During this fault condition, the module´s yellow LED will illuminate and the control panel will register a trouble condition for each addressable device which has been isolated on the shorted SLC branch. Once the fault has been removed, the module automatically reapplies power to the SLC branch.
The B224BI Isolator Detector Base is compatible with FlashScan Intelligent detectors and most CLIP mode detectors.
Isolator detector bases serve the same function as an isolator module – they prevent an entire communication Loop from being disabled when a short circuit occurs.
This is accomplished by isolating the part of the loop containing the short from the remainder of the circuit. This bases automatically restore the entire loop when the cause of the short circuit is corrected.
The B224BI base isolate the outbound side of the SLC Loop connected to terminals 2(-) and 3(+).
The base can be used to isolate branches of a Style 4 loop or to create “zones” of protection in a Style 6 Loop.
The ISO-X and B224BI are no addressable devices – i.e. they do not consume addresses on the SLC Loop. However, there is a limit to the number of devices.
Due to the current limitations of the SLC Loop of an ONYX fire alarm system, the device capacity of the loop is reduced by two (2) addresses for every isolator device in excess of 200 for FlashScan and 100 for CLIP protocols.
Also if relay or sound bases are not used, a maximum of 25 addressable devices can be connected between Isolator Modules and/or Isolator Bases.
Note: Isolator modules will not function properly when these limits are exceeded. Cosult the SLC Loop manual for more Isolator Limitation specifications.