Construction of system of video observation - from simple to complex. A part 1.

Construction of the elementary single-camera system.

The Most simple system of video observation consists of four components. The camera, the screen monitor, a power supply of the camera, commutative hardware products and a cable. We shall analyze more in detail components of system.

• the Camera is a source of video of a signal. These are eyes of system. Here for ease we consider{examine} the camera as a collection of a videocamera, a lens and an arm (and when necessary, also a housing). But at calculation of the estimate it is not necessary to forget, that at all many cameras are equipped by the built in lenses. Therefore, if you are not assured there is for the camera a lens or not - call{ring} to the manufacturer or the distributor and ask. The information on the Internet can be incorrect{invalid} or become outdated{out-of-date} (there were also such situations).
  
  
• the Screen monitor - is for mapping video signal received from the camera. Perhaps one of the most simple devices in system. But it is not necessary to forget, that picture quality directly depends on quality of the screen monitor. Though in due course at a static picture burn out any screen monitors, even LCD. In the elementary case it is possible even on a video input (LF, instead of antenna) the TV set the signal to submit - will be quite good for showing.
  
  
• the Power supply - supply of the camera (in case it{she} not 220В). In the core happen on 12В a direct current or on 24В variable. Certainly the voltage and a sort of a current should coincide with pointed on the camera. If the camera can work from any source and to use it is possible any. Preferences here are not present (though on greater{big} distances better ~24В - less loss in wires, and it is even better 220, and on an installation site of the camera - a power supply unit). In occasion of uninterrupted (standby) power supplys. They can be used in case of complete redundancy of system (the screen monitor, the recording unit, etc.) or for street cameras in housings with heating at temperatures below-10 (that have not frozen at a breakup of supply longer).
  
  
• Commutative hardware products and a cable - the Cable coaxial, connectors BNC, a cable having. More in detail on items.
  
  
  the Coaxial cable (coaxial) - is applied to transmission{transfer} of a signal from the camera to the screen monitor. The cable of postages RG-59, RG-6, SAT-703, less often РК-75 is normally applied. All of them in diameter about 6 mm also are capable to transmit video signal to distances of 250-300 m. it is Extremely desirable to not splice a cable (is on sale it{he} bays on 100м and on 295м) and if it is necessary to splice use special connectors. Application of a cable of type micro is proved at small distances and disadvantage of a place, in it{him} it is more than loss. At distances up to 2км transmission systems on a twisted pair are applied but it is already separate talk.
  
  
  the Cable having - for connection of the camera to a power supply. Generally - the more longly a cable - the more its{his} section. Normally use 2х0,5 or 2х0,75, and at absolutely small distances and CQR 2x0,22.
  
  
  Connector BNC - a connector for a coaxial cable. Bad connectors - the fundamental headache in system of video observation. Happen three sorts - under a soldering, under compression and wound. My opinion - if would be desirable without problems - that under a soldering. Then contact in the connector is guaranteed. In other cases - if there is no picture - look at connectors.

Having the equipment enumerated above we can gather the elementary system of video observation. An example in a figure{picture} 1.

Despite of a seeming ease the system in such configuration is very often used in a daily life. These are observation systems behind entrance of transport, behind technological processes or videoeyes. A principle one.

Construction of system from several cameras.

In cases when the territory of which it is necessary to watch is significant, apply some cameras. The essence of such system can not differ from resulted{brought} above, i.e. number of screen monitors to equally number of cameras. Then we shall receive one security guard and, for example, eight screen monitors. " One pie and eight candles. " Basically at the correct organization of a work station it is very quite good variant, the truth dear{expensive} and inconvenient at quantity of cameras more than four. Therefore it is necessary for us to gather video signal from all cameras and to gate out it{him} on one screen monitor. And it is better on two. Then on one screen monitor the security guard sees some small pictures (multipicture), and on the second - samples a picture from any camera. We look a figure{picture} 2.

Such device generally is named as video the multiplexer. A special case of the multiplexer - the squarer (on 4 cameras, it is the extremely rare - on 8 (two-page) though it is visible simultaneously four of them). It{he} allows to see on the screen a picture from all cameras simultaneously and-or to gate out on fundamental (or additional) the screen monitor the map from any one camera. Normally the screen shares on 4, 9 or 16 parts, sometimes on 6. According to it{this} multiplexers happen 4х, 6ти, 9ти and 16ти channel. In general all is simple.

Construction of system from several cameras with record.

For quite some time now videorecording (videorecording) of an event has ceased to be destiny of corporations and rich private traders. It became possible{probable} owing to wide application of digital videorecording units about record on a hard disk. Moreover now these recording units have the built in multiplexer and have practically superseded multiplexers from the market of security engineering. Therefore now systems from several cameras without record - practically a nonsense, in fact cost of the simple recording unit is comparable to cost of the multiplexer. Exception is made by systems of four and less cameras - many put squarers{quads} there where record is not necessary.

Also the wide circulation was received by systems of video observation on the basis of the PC. They make the fundamental competition to videorecording units.

Continuation follows...

It is added: on September, 14th, 2006