Video Transmission Methods
The purpose of the transmission medium is to carry the video signal from the camera to the monitor. Today, many video transmission methods exist: coaxial cable, fiber optic, phone lines, microwave, and radio frequency. Due to varying application needs, it is possible to find several video transmission
technologies in use within the same CCTV system.

The choice of transmission medium depends on factors such as distance, environment, cost and facility layout. In addition, nearly all methods of transmission suffer from various forms of interference or loss. The essence of good design is to minimize this impact. Examples of current video transmission mediums include:

Coaxial Cable
A coaxial cable is one that provides a continuous physical connection - or closed circuit - between
the camera and the monitor (see figure 11). The cable is shielded to minimize interference from any nearby electronic devices or electrical wires. Copper braided coaxial cable is recommended to maximize conductivity and minimize potential interference. For traditional CCTV systems, as well as many applications today, this is the most common and economical method of signal transmission over relatively short distances.

Figure 11: Coaxial Cable

Fiber Optics
Fiber optic technology changes an electronic video signal into pulsed or laser light and injects (transmits) it into one end of a glass rod (the fiber optic cable). At the other end, a receiver translates the pulsed light back into an electronic signal capable of being displayed on a monitor. The transmission is unaffected by any kind of interference, water in conduit or high voltage being run in the same conduit. Fiber optic cables have a large signal capacity (bandwidth) and no possibility of a spark from a broken fiber. Hence, there is no fire hazard to a facility even in the most flammable environment. Fiber optics offers a cost-effective method of sending large transmissions over long distances.

Telephone Line
A telephone line is a standard twisted pair of wires that can transmit the image for distances up to one kilometer without video signal boosting. This dedicated line connects the transmitter (camera end) with a receiver (monitor end). Through the use of specialized transmission and receiver equipment, it is
possible to use standard telephone lines for video signal transmission.

Microwave
If already in place, microwave can be a very efficient and cost-effective method of delivering black & white or color video. Microwave turns the video and data signals into high radio frequency signals and transmits them from one point to another via free air and space. A receiver then converts the transmission back into the video and data signals and displays the scene on a monitor. Good quality transmission can be achieved over a line of sight path (see figure 12). Microwave technology offers a large bandwidth to carry video, however, it can be affected by environmental conditions. It is a practical option when a wire path between the camera and monitor locations cannot be established or is prohibitively expensive. Microwave transmission is regulated by the FCC, and a license is required.

Figure 12: Microwave requires a line-of-site transmission.

Radio Frequency
Radio frequency (RF) is a reliable, but short distance, line-of-sight video transmission technology. It is becoming increasingly popular where hardwiring methods are either impossible or impractical, and has been used successfully to reduce cabling costs even within large buildings. Environmental conditions or other RF in the area can affect it.

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