Useful Information
- ♦ Application
- ♦ Cameras
- ♦ Lenses
- ♦ Light & CCTV
- ♦ Number Plate Recognition
- ♦ Thermal Imaging
- ♦ Housings
- ♦ Digital Images
- ♦ Digital Technology & Recording
- ♦ Video Compression
- ♦ Infrared
- ♦ IR & LED Lighting
- ♦ IP CCTV & Technology
- ♦ Monitors
- ♦ Motion Detection
- ♦ Multiplexers
- ♦ PIR Movement Sensor
- ♦ Remote Positioning Devices
- ♦ Video Motion Detection
- ♦ Police and Standards
- ♦ Multiple Screen Display
- ♦ Signal Noise Ratio
- ♦ Survellance Vechicle
- ♦ Three-dimensional (3D) design in CCTV & Security
- ♦ Transmission of Video Signals by Cable
- ♦ Transmission of Video Signals by Remote Methods
- ♦ Transmission of Video Signals by Fibre Optics
- ♦ Video Analysis
- ♦ Wireless CCTV
Transmission of Video Signals by Remote Methods
There are many instances where it is not possible or desirable to use cable and other methods need to be employed. These can be:
* Infrared beams.
* Microwave.
* Public telephone networks.
* High Speed Data Links
* Local Area Networks (LAN)
* Wide Area Networks (WAN)
* Optical fibre cables.
The choice will depend on the final system requirements. This may frequently be coupled with the different cost of several options. In addition, the level of security and continuity of use will have a bearing on the final selection.
With all these systems, it is imperative to study the supplier’s information extremely carefully. For instance, there was a slow scan system that described the picture update time as 20 seconds full picture, 5 seconds quad display. What this really meant was that in quad display one picture was updated every 5 seconds. It still took 20 seconds until the first picture was refreshed! Wherever possible see a demonstration of a system on a customer’s premises. Look carefully at the resolution versus the refresh time.
Free space transmission
There are frequent situations where there is no possibility of making a direct cable connection between the camera(s) and the control position. This particularly applies when real time continuous monitoring is required. A situation needing this approach would be where, for instance, there is a main road between the cameras and the control.
Another situation would be when the two ends of the system are separated by a wide river such as in London. It could be a large industrial site where the cost of cabling would be prohibitive.
Free space transmission consists of a transmitter at the camera end and a receiver at the control end. All free space transmission systems require that there be a direct line of sight between the transmitter and the receiver. Normally there are one transmitter and one receiver for each camera.
All types of free space transmission equipment must be very rigidly mounted. This is especially important if the transmitters or receivers are to be mounted on masts or poles.
The distance between the two locations is critical to the choice of equipment. The manufacturer’s specification must always be respected. Performance can deteriorate exponentially if their recommendations are exceeded. A 10% increase in distance could result in a 30% fall off in performance.