Wireless-camera:selection of video signal transmission methodHome > Camera Equipment > Video Signal Transmission
Wireless-camera or Cable camera? Which one is better?
Wireless-camera or Cable camera connections are two of the most used means to transfer to the viewer the images that are captured by the Surveillance Camera. Before selecting anyone of them, one should grasp the main differences that we are going to present hereafter. The important challenge, for any transmission method, is to be able to pass on the video signal with high fidelity, with minimum disturbance caused by surrounding interferences, from the source, either a Wireless-camera or a Cable camera, to the end user. The function of sending Video signals over a physical distance to the displaying instruments used to view them, is performed by different means depending on the transmission method selected. The viewing instruments, whose details we will examine in another page, are variously called monitors or screens. Given the wide selection of transmission technologies, one has to examine features and benefits of the different types to decide, in the particular case, which one is most suitable to perform the required surveillance function, satisfactorily and at the minimum cost. Many video transmission methods exist: coaxial cable, telephone lines, cat5 (category 5) wires with adapters, fiber optics, microwave, and radio frequency. Due to varying application needs, it is possible to find, in complex outfits, several video transmission technologies in use within the same CCTV system. However, for simple home surveillance purposes, the practical choice is probably limited to either coaxial Cable or Wireless-camera (radio) transmission.
Coaxial Cable For traditional CCTV systems this is the most common and economical method of signal transmission over relatively short distances. Cables of this type are available, if this option is selected, that include under the same sheath also a pair of copper wires for supplying power to the camera. This solution merits some attention if the Cable camera is located far from mains outlets. Characteristic impedance is determined by the size and spacing of the conductors and the type of dielectric used between them. A 75 ohms coaxial cable is used generally to carry video signals. Although more expensive than standard telephone wire, coaxial cables are less susceptible to interference and can carry much more data. For short runs under 200 feet (60 meters), RG6 coaxial cables can carry the video signal between the camera and the monitor. For distances over 200 feet, the RG59 coaxial cable should be used. Although rarely used for longer distances, it's still the ideal cable to carry low frequency video signals from a camera up to 1500 feet (460 m). If opting for coaxial cable transmission, one should procure the required length of cable and the required adaptors to connect to the camera at one side, and to the monitor or other device at the other side. The cable must be laid down and fastened with proper clips along the path, holes may be required in walls and passages. This operation, although simple in principle, may need be performed by an expert technician. The advantage of coaxial cable transmission is that the installation is robust and lasting, generally independent of weather conditions. The limitation however is that any future layout modification or displacement of either device is cumbersome, requiring a new length of cable or at least the repetition of the lay down procedure along a different path. The cable, if easily accessible, may be a weak spot readily interrupted by hostile people to prevent continuing surveillance. If there is danger that a visible cable be cut to stop transmission it should be hidden or hardened. Wireless-camera The video signal from the Wireless-camera is sent by radio at the common frequency to the receiver which is connected by traditional means to the other elements of a surveillance system. Radio Frequency (RF) is a reliable though short distance video transmission technology. It is regulated by national authority. For limited power dedicated installations, no special authorizations are required. For longer range and best reception unobstructed line of sight should be preferred, although normal walls are not an obstacle. The main advantage of a Wireless-camera system is that no coaxial cables have to be installed so that less labor is involved. Thus it is easy and practical to displace the elements to a new location, should the need arise. It is similar in principle to the familiar wireless phone (apart from the directional antenna). Another advantage, possibly important when monitoring of high value objects, is that the recording device is out of sight, hidden somewhere, difficult for intruders to locate and destroy. However the Wireless-camera, to be operated, still needs power, generally by wire from a low voltage power supply, an adaptor (transformer) plugged in a regular outlet located somewhere near the camera location. (The battery solution is not recommended due to the short time between battery changes). The use of a Wireless-camera is becoming increasingly popular where hardwiring methods are either impossible or impractical, and has been used successfully to reduce cabling costs even in large buildings. Environmental conditions in the area may affect its performance. Click on the following, for a complete set. If more than one Wireless-camera is needed, the number of available frequencies may limit the number of Wireless-cameras that can be deployed. If only four different frequencies can be used then only four cameras can be installed at a given location. The three different radio frequencies most used are:
Within each one of them a few different channels may be provided to avoid interference with other devices present nearby using the same frequency. A radio transmission of signals can be disturbed by interference either occasionally unavoidable (By competing devices on the same frequency) or generated on purpose by an interested party to disturb or disrupt continuing surveillance operation. One must remember that the transmission path can be attacked: in case this is a real danger, suitable measures should be taken to protect the integrity of transmission. Although probably not a worry for home surveillance uses, it should be noted that Camera-wireless transmission can be subjected to eavesdropping. In summary one can note that any Wireless-camera can be used almost anywhere but the most common ones are for covert or hidden video surveillance, baby sitter camera, entrance door control and the like. The choice of transmission medium depends on factors such as distance, obstacles, environment, home layout and cost. Also the option of future mobility should be considered. In addition, nearly all methods of transmission suffer from various forms of interference or loss that should be minimized by good design. In our pages for selection recommendations, we point to one wireless solution for a simple surveillance case, and to wired solutions for all the other cases.
When finally going on to select the elements forming the home surveillance package it is important to make sure that the selected transmission means are indeed compatible with the hardware and that the required terminals are procured for closing the actual connections. Explore the following
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