The external perimeter protection is the first and most important element in the creation of an intruder alarm system. The interconnection cabling associated with the detectors for this system is therefore more critical than that for internal systems because of the following factors: length, accessibility to unauthorised people, exposure to environmental disturbances or damage. For external perimeter security system serial bus cabling has enormous benefits when creating a cabling configuration for a security system.
By De Astis Vincenzo
WHAT ARE DETECTORS?
The detection of unwanted intrusions, on sites where the risk is not considered negligible, is achieved by using electronic devices that analyse the physical effects created by the intrusion in the area where the intrusion is attempted or on the protective structure that circles the building. These devices are called ¡°Detectors¡±.
The detectors are therefore the components of an electronic security system whose essential task is to produce the threat information, representing the primary element of information which the central event processor combines with the current operational status, activating the predetermined response to that event. This primary element of information is called an ¡°Alarm¡±.
As well as generating alarm information the detector must generate additional information relating to attempts to interfere with the device and the integrity of operation. These two additional elements of information are known respectively ¡°Tamper¡± and ¡°Fault¡±. Thanks to the advanced analysis technique of ¡°Fuzzy Logic¡± which CIAS detectors have been using for 20 years, significant increases have been achieved in the Probability of Detection (PD), accompanied by an equally significant reduction in the False Alarm Rate (FAR), properties that complement one another, with an increased ability to recognise attempts to defeat the detector make these the best performing and most advanced detectors in this sector.
Obviously the amount of information produced by these detectors is far greater than that made up from the previous three events: alarm, tamper and fault. This additional information is extremely useful, both in the active phase and the maintenance phase of the system. The maintenance of a system is the single measure that ensures effective operation over time and therefore simple maintenance and effective performance is the best guarantee that a detector will be able to perform its job continuously.
TRANSPORTATION OF SECURITY DATA
It is obvious that the transportation of security data, however big or small, is somewhat critical, particularly in relation to manual tampering and corruption due to interference.
Therefore, the simplest method of transportation (copper pairs), results in something that is expensive in terms of the number of cables that must be installed as well as being extremely vulnerable to induced interference or tamper attempts and the total inability to carry supplementary information compared to a Serial Bus. In fact the Serial Bus is independent of the actual physical method used (copper twisted pairs, Fibre-optic, Ethernet network, Radio, Mains electricity supply network) and provides services for the level of transport and the level of the application.
Suitable checks, inserted in the protocols of the transport and the application, guarantee that the recovered information is not corrupted by interference (Cyclic Redundancy Check) or by attempts to substitute the communicating devices (Message Signatures). In addition the bidirectional nature of the bus allows various checks and adjustments to be carried out (sensitivity, date/time synchronisation, etc.) or to send commands (Test, Stand-by, etc. )to the detectors in the field.
The external perimeter protection is the first and most important element in the creation of an intruder alarm system. The interconnection cabling associated with the detectors for this system is therefore more critical than that for internal systems because of the following factors: length, accessibility to unauthorised people, exposure to environmental disturbances or damage. For external perimeter security system serial bus cabling has enormous benefits when creating a cabling configuration for a security system.
As far as the length is concerned, whatever physical method of transport is used to carry the information, which is digital, the serial bus is the least dependent on the distance between the detector and the center. As for unauthorised access, the protocols used (Polling and Signature) prevent most, if not all, attempts. As far as exposure to environmental disturbances or damage, such as lightning or differing ground potentials, these can be almost totally eliminated by the use of fiber optic cabling, which ensures perfect electrical isolation between the communication devices.
WHAT IS IB-SYSTEM-RACK?
CIAS Elettronica have designed the IB-SYSTEM-RACK, a cabling system equipped with all these features, to which can be added, using versatile field components, called IB-FMC-Rep, the possibility to carry data using the most efficient medium possible (copper, fibre, Ethernet, radio) and to adopt various architectures (bus, star, closed loop, mixed). The IB-SYSTEM-RACK allows, directly or via appropriate interface units called IB-Transponder, the delivery of information from all types of detectors (analogue, digital, with traditional processing, with ¡°Fuzzy¡± processing) to the central location where the status of the detectors is made available in the form of normally closed relay contacts which can be interfaced into any type of alarm monitoring system. In practice this provides a concentration of the alarm, tamper and fault relays for each detector at a central location making it extremely simple to connect to central alarm management system. This task is achieved by using RS 485 serial lines for each system (up to twelve) or fibre optic lines (up to four) or connection to an Ethernet network or connection to a wireless network. With the IB-SYSTEM-RACK the type of network, the configuration architecture and the length do not represent any limitation. Using the IB-FMC-Rep or Bus-Rep devices with converters, regenerators, and repeaters for the specific medium makes it possible to create a Bus architecture of almost any length, with a much greater number of devices than is possible with standard RS485 and with a physical architecture that can be completely stellar.
With the aid of the IB-FMC-Rep field devices, equipped with a fiber optic interface, it is possible to obtain a complete electrical isolation between the detectors and the central location and between the different detectors. In this way, as well as avoiding electromagnetic, electrostatic and ground potential interference which can corrupt the information or cause faults on the equipment, it also makes it extremely difficult for anyone to access or manipulate the data without the correct authority and access. With these devices it is very easy to configure a fiber optic Self Healing Ring, which gives a double redundancy, guaranteeing maximum resistance to faults. With the basic version of the same device, it is possible to create the same ring structure using copper pairs. This also provides optimum resistance to faults. In both cases faults on a detector or an IB-Transponder interface are not propagated (effectively isolating the fault) and therefore has no effect on the rest of the data that is being carried. If the IB-FMC-Rep are equipped with an Ethernet interface it is possible to use all the advantages of the infrastructure without any degradation to the data rate (20 Kbit/sec per system connected) making it possible to connect multiple systems to the same architecture. Access to an Ethernet network can also be achieved via a wireless connection by the simple connection of an IB-FMC-Rep, equipped this time with an Ethernet interface to a standard wireless access point with obvious advantages of simplicity and control of the structure and wiring costs.
By using the specialist software such as IB-TEST and IB-TEST-Map it is possible to display the status of all the connected detectors. With the WAVE-TEST software it is also possible to collect and manage a lot of information that ¡°F uzzy¡± detectors (Armidor, Ermo482X Pro, Manta, etc.) produce as well as sending commands to check and adjust the operating parameters.
This system allows the cabling and transportation of information from a number of detectors to small systems to very large systems. Using the IB-SYSTEM-RACK the information relating to the status of a single detector or a group of detectors can be extracted at one or many points on the network allowing a very diverse method of management. It is possible to extract information, as well as at the central location, in the field, which can, for example, activate a distributed video recording system, activate lighting for CCTV cameras or activate presets on dome cameras to capture images from different parts of the intrusion system.
With this simplicity it is possible to design a cabling system for small perimeter protection systems for small houses or buildings as well as large protection systems for industry, power generation sites, military sites or even enormous intrusion systems for country borders.
De Astis Vincenzo is Technical Director of CIAS Elettronica S.r.l. (www.cias.it).
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