Posted by Arowosegbe Olawale in General

Connecting the cameras and other CCTV parts in a wired system requires cables. There is less chance of interference with wired transmission, allowing for clearer video. It is not necessary to place cameras in close proximity to any monitoring or recording devices. Coaxial cables, UTP cables, and fibre optic cables are the three most popular wired options for today's CCTV systems. Despite the cyber security risks associated with an open network, some CCTV systems still rely on transmission over a public telephone network.

4.1.1 Coaxial Cable

The most typical method of connecting a camera to a TV or other CCTV device is via coaxial cable. The components of a coaxial cable are a single wire, an insulating layer (dielectric), a shield of braided wire, and an outer sheath of plastic or rubber. The diagram for this building can be found in Figure 4-1. Keep in mind that the highest quality cable is needed for CCTV applications. Copper is required for both the central conductor and the braided shield. Some consumer cable applications use a shielding technique involving aluminium foil that does not satisfy CCTV standards.

Direct-run distances up to 2,000 feet are possible, depending on the cable's gauge. It is possible to extend the length of a cable to reach a further location; however, this will necessitate the installation of amplifiers along the line leading from the camera to the display device.

Reliability and picture quality can be negatively affected by low-quality cable. Due to the electrical nature of coaxial cable transmission, RFI and EMI can disrupt the signal. The video signal can be intercepted either through these emissions or by physically tapping into the cable.

When using coaxial cable or any other method to transmit an electrical signal, it is imperative that the entire CCTV system be properly grounded. Inadequate grounding of equipment and cabling can cause video to be distorted, cut off, or become grainy.

Figure 4-1. Coaxial Cable Construction

4.1.2 UTP Wire

There are situations where using coaxial cable to connect a camera to a monitoring station is impractical, but existing telephone wire can be used instead. In many older structures, for instance, there are unused telephone lines (called UTP) that could be put to use in a video distribution network. As a result, you save money in the long run, aren't as worried about ground loops, EMI, or induction, and can use this with minimal effort. The weight and size of telephone wire are significantly less than that of coaxial cable. It's important to note that if you want to use an abandoned phone line outside of your building's walls, you might need to go through some paperwork and sign a service agreement with the phone company first.

Both wires in UTP are twisted together to form a single strand. These wires typically have an American wire gauge (AWG) of 22 or 24. Unshielded twisted pair is an option for video transmission, but it should only be used to connect a single camera to a display or other device. The twisted pair can only be used with one specific video camera. Although the price of twisted pair wire per foot is less than that of coaxial cable, signal conversion devices (transmitter and receiver) must be installed at both ends of the wire run. The maximum recommended length for a twisted pair wire run is 5 kilometres. Extending the reach of twisted pair requires placing repeaters at regular intervals of at least 4,500 feet.

Similar to other forms of electrical transmission, UTP could be intercepted or otherwise compromised by interference or other illegal means. Having to go through a central office to connect wires slows things down. Using "punch down blocks" or splices, this kind of wire is best suited for constant point-to-point transmission. It's crucial that all of the links be rock-solid and completely resistance-free.

4.1.3 Fiber Optics

The lightweight fibre optic cable consists of a single spun glass or plastic fibre or a group of such fibres encased in a protective sheath. Its large bandwidth makes it ideal for transmitting video signals. Without amplification, fibre optic cable can be employed for distances up to 6 miles. The camera's video signal must first pass through a fibre transmitter that converts electrical signals to light impulses. At the opposite end, a fibre receiver is required for signal conversion back into electrical signals.

The optical fibre cable is resistant to RFI and EMI. In addition, grounding is not an issue with fibre optics, and the cable is less susceptible to lightning strikes, if not immune. In addition, fibre optic cable has a high cost-to-performance ratio in systems constructed with premium components. A single strand of single mode fibre can transport 32 analogue video channels. The expense of fibre optic cable may not be justified in low-end systems. Installation of fibre optic cable requires extreme precision, as even minor cable damage or sharp bends can significantly degrade the signal.

4.1.4 Telephone Network

The telephone network is an additional option for wired video signal transmission. Standard voice grade telephone lines lack the bandwidth to support real-time, full-motion video, but they are still useful for specialized CCTV applications. However, when video security is a concern, telephone lines are not recommended due to cyber security vulnerabilities. 

Figure 4-2. Telephone Network

Slow-scan video imaging is used in some forms of CCTV technology. Slow scan video, in contrast to the more common 30 frames per second, skips some of the images in the video at will. Further, the image quality may be lower than that of a typical video. This mode of transmission can benefit greatly from the use of digital compression.

As data compression methods continue to advance, it is now possible to send video images efficiently over a phone line. At the current rate of 28.8 kilobits per second, a single video image can be sent every 6 to 12 seconds over regular telephone lines (Kbps).

ISDN phone lines have a greater bandwidth than analogue lines because they combine two 56 Kbps channels into one 112 Kbps one. With such a rapid rate of data exchange, a single video image can be sent in about a second.

T-1 lines and Fractional T-1 lines are also available for those who need a higher transfer rate. When multiple 56 Kbps channels are combined, as is possible with the T-1 family of technologies, much higher bandwidths can be attained. T-3 or E-1 lines, with their enormous bandwidth, may be able to handle the data needs of extremely large CCTV networks.

4.1.5 Category 5 Cable

Video is transmitted over a network using a Category 5 cable. The cable uses four pairs of 24-gauge copper wire twisted three times per inch to create a UTP configuration. Crosstalk, or electromagnetic interference, is minimized thanks to the high twist density of the cable. It's possible to transmit data at speeds of up to 1 Gigabit per second over Category 5 cables, which can carry frequencies up to 100 MHz (Mbps). The RJ45 plugs at the end of the cables ensure that they are compliant with the Electronics Industry Alliance/Technology Industry Association 568 Commercial Building Telecommunications wiring standard.