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american safe - analog camera

Analog Cameras

Analog cameras can record straight to a video tape recorder which are able to record analog signals as pictures. If the analog signals are recorded to tape, then the tape must run at a very slow speed in order to operate continuously. In order to allow a 3 hour tape to run for 24 hours, it must be set to run on a time lapse basis which is usually about 4 frames a second. In one second, the camera scene can change dramatically. For example, a person could have walked a distance of 1 meter. Therefore the distance is divided into 4 parts, 4 frames, or 'snapshots' in time. Then each frame invariably looks like a blur, unless the subject keeps relatively still.

Analog signals can also be converted into a digital signal to enable the recordings to be stored on a PC as digital recordings. In that case the video camera must be plugged directly into a video capture card in the computer, and the card then converts the analog signal to digital. These cards are relatively cheap, but inevitably the resulting digital signals are compressed 5:1 (MPEG compression) in order for the video recordings to be saved on a continuous basis.

Another way to store recordings on a non-analog media is through the use of a digital video recorder (DVR). Such a device is similar in functionality to a PC with a capture card and appropriate video recording software. Unlike PCs, most DVRs designed for CCTV purposes are embedded devices that require less maintenance and simpler setup than a PC-based solution, for a medium to large number of analog cameras.

Some DVRs also allow digital broadcasting of the video signal, thus acting like a network camera. If a device does allow broadcasting of the video, but does not record it, then it's called a video server. These devices effectively turn any analog camera (or any analog video signal) into a network tv.