Extra Low Voltage system (ELV)
ELV is the terminology used in the construction world in an attempt to electrically define all the systems in a building which need electricity to run but are not part of the building’s main electrical system. ELV covers all the new modern technologies that are increasingly becoming must-have systems in every building such as data network, CCTV, public address systems, audio/video solutions and access control.
LAN and WLAN
LAN stands for Local Area Network – also known as SCS (Structured Cabling System). Simply put, it is the data cabling in the building to enable users to network their computer devices and possibly access to internet. In a small building, this can be simply CAT6 cabling from an MDF (Master Distribution Frame – i.e. equipment rack) while in larger infrastructures, you usually see multiple IDFs (Intermediate Distribution Frame) interconnected by fiber optic cables. WLAN stands for
Wireless LAN which is the network of wireless access points that provide wireless network coverage within and outside the building. As you will see below, as the technologies enhance, more and more other ELV systems depend on LAN infrastructure of buildings.
While up to some years ago, analog telephony systems were still commonly used in buildings and were setup by using multi-pair copper telephone cables connecting the PABX (Private Automatic Branch Exchange) to telephone sets, they are now almost totally replaced with VOIP (Voice Over IP) solutions that require no separate cabling and depend on the building’s LAN infrastructure for the interconnections.
CCTV stands for Closed Circuit TV (again a very old acronym which shows the old “electrical” roots of such systems). Simply put, these are the camera systems setup inside and outside of buildings to provide monitoring surveillance. Old analog cameras used a separate cabling of coaxial cables connecting each camera directly to the DVR (Digital Video Recorder). These are also today almost totally replaced with IP Cameras utilizing the common LAN infrastructure of the building.
ACS is the abbreviation for Access Control System. ACS systems give access to different building locations (usually implemented by automatic unlocking of doors) through different means of authentication of people (by magnetic or RFID identification cards, by finger print, IRIS or face recognition). Almost all new ACS solutions also rely on LAN infrastructure to some extent, while they also include electrical cabling to magnetic door locks, manual push buttons, and magnetic sensors installed on the doors and entry gates.
PAS / PAGA
PAS (Public Address System) or PAGA (Public Address and General Alarm) is the speaker system installed in buildings for making announcements, playing background music and broadcasting pre-recorded alarm notifications, sometimes automatically triggered by fire alarm systems. PAS is probably one of the few ELV systems that is still not much IP based and use twisted-pair electrical cables for connecting the distributed speakers to the power amplifiers. However most of newer PAS systems have accessories to enable utilizing LAN infrastructure for interconnecting the main components and provide a distributed design.
SMATV / CATV / IPTV
SMATV (Satellite Master Antenna Television), CATV (Cable Television), and IPTV (IP Television) all explain different technologies to provide a TV distribution system within a building, interconnecting multiple television sets to a single source (usually called Head End) so each television can select the desired watching channel from a selection list. While SMATV and CATV have their separate cabling network based on coaxial (or sometimes fiber) cabling, they are rapidly being replaced with IPTV solutions which rely on the same LAN infrastructure jointly used by other systems.