Wednesday, October 28, 2009
Getting the picture signal from the camera to the monitor, recorder or TV.
The most common method used on professional installations is RG59 Coaxial cable. The centre core is the signal conductor while the outer shield protects the signal from electro-magnetic interference. It is a low-loss cable which will allow cable runs of up to 250 metres. Longer cable runs can be achieved with the use of a video amplifier.
BNC connectors are the preferred type of connector in professional CCTV installations and are recommended by 2seetv for all DIY CCTV applications. The connectors twist and lock together giving secure connection.
Professional switchers, multiplexers, monitors etc. will all use BNC connectors. If you are connecting to a domestic TV or VCR you will need to convert to phono or SCART connectors. Simple adapters are available and are supplied with many of our kits.
Increasingly popular for CCTV installations is the use of RJ45 composite cables. These look similar to a telephone extension cable but are terminated in a RJ45 connector. A simple adaptor is used to provide a BNC, Phono and a 2.1mm DC power plug connector. This means that one cable can be used to carry the video signal, audio and DC power.
This type of cable is more flexible than RG59 cable and its small size makes it suitable for running along the top of a skirting board or around a door frame.
Many DIY CCTV products do not use coax cable and BNC connectors. The cable is more expensive and the connectors are difficult to fit. We can supply a range of ready-made coax/BNC cables that price match most RCA/Phono type cables.
It is advisable to keep cable runs as short as possible. Most of our camera kits offer a choice of cable length at no additional cost. Unless you are experienced in refitting a crimped BNC connector we do not recommend you cut the cable. Before ordering a camera kit measure the required cable run. Select the required cable length from the drop-down box. BNC cables can easily be joined together with a coupler such as CCA-005.
High-quality cameras with anti-mist coating, CCD lenses will give clear, crisp, noise-free pictures. It is essential to use good quality cable if these images are not to deteriorate. For CMOS cameras the quality of cable is less important.
Increasingly popular is wireless transmission. Government regulations now allow licence-exempt systems that can typically transmit signals up to 100 metres in line of sight. This reduces to approximately 30 metres when used indoors. Simple wireless cameras will only work on one frequency so you cannot use 2 such products within 100 metres of each other. Cameras and receivers are available with 4 selectable channels making multi-camera systems feasible.
Even the small covert type of camera can be supplied with its own built-in transmitter. Alternatively, any camera can be connected to a stand-alone transmitter.
Remember that CCTV cameras require power to operate. The voltage is usually in the range 9-12V DC and this is typically derived from a small power supply plugged into the mains supply. So "wireless" does not mean totally "wire-free". Battery operation will be measured in hours, so is not suitable for permanent installations. However, it is often easy to pick up the power for the camera in some areas such as the loft of the house. Wireless systems are great where it would be difficult to run the video cable back to VCR or monitor.
Wireless transmission is also useful for temporary monitoring of an office or reception area. The miniature wireless cameras with battery power can be fitted to model aircraft or model trains. The receiver can be connected to a domestic camcorder to recorder the "ride-on" experience.