Analog systems
The Analog systems are the oldest, the simplest, most inexpensive and last but not least, most reliable video surveillance systems. An analog surveillance system consists of monitor, recorder, multiplexer and of course cameras. TV monitors are analog devices, which displays a video signal. They are not anything more than a TV with high resolution. These are the only devices that can reproduce the screen image of analog cameras for video surveillance systems. When you add a multiplexer, a monitor can depict 4, 9 or 16 video signals.
Recorders or recorder - with them you can record video signals from a camera, or by multiplexor - through several cameras on a standard VHS cassette. Some of these recorders can be made to record 960 hours on one tape, but this means that it records one shot every 9 seconds ... In practice it has imposed a standard and videotapes are used in the recording mode in which 3 days of video are stored on one tape. In this mode, a shot is made every 3 seconds. Given that the technology is about 20 years old, it is considered an acceptable result.
Reproduction is something very important in video systems - so when video recording in extended recording mode, a recorder with extended recording (time lapse recorder)should be used for playback. Standard video recorders, to be found in almost every home, can not handle extended format record and can not usefully play. Recorders with extended recording use standard 3 hour cartridges, so that 10-12 cartridges in recording mode of 72 hours will provide a record of more than 30 days. The video signal from each camera is usually transmitted by coaxial cable to multiplexer. Also coaxial cable connects the multiplexer to monitor. Cord from the VCR out of the multiplexer is connected to the entrance of the video recorder and another from V out of the recorder is connected to the VCR in of the multiplexer. The system is programmed through the control panel of the recorder and multiplexer. Program options are displayed on the monitor. In playback, recorder submitted video signal in a specific format to the multiplexer, a monitor then receives recorded information from several cameras.
ADVANTAGES:
1. As mentioned above the system is very reliable because of its simplicity and it does not require special skills to operate.
RESTRICTIONS:
1. Quality is considered low compared with that of digital systems.
2. Tapes should be changed regularly. Recorder must be cleaned and maintained.
3. Over time, the recording quality is worsening.
4. Systems can not be networked and does not provide remote monitoring.
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