To discover the components of surveillance system is a confusing, but necessary, issue. To know all their characteristics, functions and possibilities is something essencial to get our goal: increase the security.
En este artículo nos detendremos en alguno de los elementos del sistema CCTV para ver sus prestaciones y las diferentes opciones existentes. Una pequeña guía para entender si un presupuesto se adapta a nuestras necesidades o no.
In this article we´ll see some elements of CCTV system to know their feautres, and different options. A little guide to understand if a quotations is adapted to our needs or not.
YOUR CCTV CAMERA
Cameras are one the components visiblest of a CCTV system. The technologic evolutions has been so fast, so now we could find endless options. We are going to show the feautes you have to keep in mind when we look for our camera:
- Power supplying: we could find cameras that work to 200VCA, 24VAC or 12VCC. We have to be care of this info to don´t have a mistake.
- Sensor kind: we have to know about CCD sensor, catch white/black signs, and CMOS that catch white, black and infrarred signs.
- Resolution: it calculates the quality of the details are watching, it means, the image definition. The standard resolution of a CCTV camera is 420TVL (TV lines) it´s above the average of cameras.
- Film Speed: it informs about the minium light we need to get a video sign. It measures by LUX. We have to think where we fix the camara and what we want to record to choose a goof film speed.
- Lents: to know wich lent is perfect us, we have to know the distance between camera and place recorded, and the light of the area. We could distinguish:
- Fixed iris: to cameras located outside where light is stable.
- Manual variable iris: to cameras located inside where the light could change.
- Autoiris: it´s perfect to cameras located outside, where they auto- adjust to get always a good quality, ilumination doen´t care.
- Fixed lents: we choose them when we know perfectly that this lent is correct. After that, it couldn´t be changed.
- Varifocales: cuando el campo de visión es inseguro y debemos colocar primero el sistema para definirlo, recurriremos a las cámaras varifocales. Éstas permiten modificaciones posteriores.
- Varifocal lents: when the recorded area isn´t clear, first we have to installa a system to define it, that we´ll get varifocal cameras. They allow to do following changes.
- Zoom: Perfect cameras when we need to take close and far images alternately.
VIEW OF IMAGES
Otro de los componentes esenciales en el sistema de CCTV son los monitores. Sin tener tantas opciones como en las cámaras, hay varios elementos que debemos tener en cuenta. La división básica que nos encontramos son:
Other important components of CCTV system are the sreens. There aren´t many options like cameras, but there are some element that we have to keep in mind. Basic divison is:
- Black and white: this sreen give us a better resolution.
- Colour: with this screen we´ll watch the things better.
If we need to watch a lot of details, we´ll need a great resolution, that we´ll select a black/white screen. But if we want to identify things and/or people, we´ll get a colour screen.
Sreen size is a element to keep in mind. Measuring is made by inches and we keep in mind the screen diagonal. The sizes most used are the 9″ (23cm) and 12″(31). Also there are smaller screen, 5″ and 7″, to watching systems.
We could watch some cameras in the same screen if we use QUAD compressor and multiplexor. This technology digitalises the imagen and after that, each imagen is compressed in each existing quadrant. The sign is synchronised and we could watch at the same time, 4 different cameras.
IMAGE TRANSMISSION
CCTV system has different components conected each other. It doesn´t mean that all wires are correct, anywhere is good to put wires, or you need wires in your installation.
So, transmission could be done by:
- Coaxial wire: this cable avoids elctromagnetic interferences beyond 50kHz. If we use this wire, it has to be fixed, minimum, 30cm apart others. Interference is showed with horizontal lines that cross the screen from the end of it until its top.
- UTP wire: it used to installations where the distance beteween components is 200 meters and more. A wire could connect until 4 cameras. If we use it with system where needs 70 meter of wiring, we´ll reduce the cost of instalaltion.
- Wireless link: this system allow a good transmisson along 100 and 800 meters. Usual frecunecy is 1Ghz and 10GHz. Although a 6Mhz or 7Mhz is enough to get a good quality.
RECORDING EQUIPMENT
We have two big groups of recording equipment:
- Analogue: although we have a system that records digitally, we´ll have an analogue system if the image transmission is made by wire.
- Digital: we could watch the images from anywhere and don´t need to wire a screens network.
If we add some components like multiplexo, we could see until 32 cameras in the same screen. Everythin at the same time.
ESSENTIAL FEATURES
These are the essential faeatures you have to keep in mind when you go to choose the CCTV components:
- How many cameras you system accepts?
- How many images per second could the system record?
- Storage capacity.
- What is the input to audio recording?
- Movement detection.
- Recording by date, day and hour.
- Alarm input.
- Images sizes: 160x120px, 320x240px, 640x480px.
- Types and number of output
- Remote connection by networr: web browser or client software.
- Recording speed options.
