Transmission of CCTV Video Signals
About Cables
How the video signal is transmitted from the camera to the control point is usually determined by the most effective means available. Not all applications can use or should use the same method for transmitting the video image.
Coaxial cable
Coax is the most common method of transmitting the signal. It provides very high bandwidth and assures the transmission of high quality video within its distance parameters. It is restricted, primarily by distance and the quality of the cable used. Coaxial cable has proper electrical features to transmit the video signals from the camera to the monitor. Among various coaxial cables, RG59/U is most common with a 75-ohm impedance and can be installed up to 450ft distance without loosing the video quality. This cable is usually connected by BNC connectors at both ends.
Twisted pair
This method requires the use of a pair of twisted wires to carry the video image. Since the redevelopment and upgrade of twisted pair technology in the early 1990s, twisted pair transmission technology is fast outpacing coaxial cable.
Fiber Optics
Fiber is clearly the best method for transmitting video over longer distances. When using fiber, the video signal is electronically changed into pulsed light. This light is then injected to a fiber. At the other end of the fiber, the pulsed light is changed back into an electronic signal. The advantages of fiber are that the video signal can be sent over long distances without significant degradation. Fiber-Optic Cable is not affected by electrical interference and has no problem even in contact with high-voltage power. It transmits video signals with extremely high efficiency and can run up to miles. The problem is that it is expensive and difficult to handle.
RCA Cable
RCA cable is not standard in the industry but is used a lot, specially for short distances up to 250ft. Twisted wire from 14 to 24 AWG (American Wire Gauge) with RCA connections at both ends will work as RCA cable. Even though its transmission quality is not as good as Coaxial Cable or Fiber-Optic, RCA cable is widely used because it is very easy to handle and has no problem of loosing video signal up to 250ft distance.
DIN Cable
Most observation systems which are pre-assembled at the factory have DIN cables with DIN connectors at both ends. DIN cables have 5 or 6 wires inside the configuration of which is, for example; wire 1 is for video, wire 2 is for audio, wire 3 is for power(12VDC, positive), wire 4 and 5 are for speaker(positive and negative), wire 6 is for ground. Mini DIN cable, which is used for mini camera package, comes with 4 wires inside. DIN cable, large or mini, can run up to 250 ft distance without loosing the video quality
Microwave
This is the use of microwave radio waves to transmit the video signal across areas ranging from 200 meters (short range) to ten miles (long range). In the US, microwave systems over 100 mili- watts must be licensed by the FCC in advance of installation. Microwave systems must have an open line-of-sight between the transmitter and the receiver.
WAN Digital transmission
The introduction of the internet in the mid 1990’s opened the door for wide area control and monitoring systems within the CCTV industry. Used by large corporate entities, a single control point is now able to monitor activities at multiple points around the world. Wide area networks can be built using private network communications paths, or use the Internet as the communications medium. Major disadvantages of intranet transmission include bandwidth restrictions and potential interference or security breaches from hackers.
Cable Ties
Because the transmission of video signals is directly related to the spacing between the inner wires or conductor and shield, any changes in the distance between the wires or conductor and shield will degrade the picture quality. This change may be caused by tight bends, kinking, indentations, stapling or others. That's why you need to use suitable cable ties and cable management when working with Coaxial Cable or DIN cable.
What is RG?
RG stands for military specs Radio Guide (which is old and meaningless anymore) and the RG numbers are kind of arbitrary. The most common RG designations seen these days are RG-6, RG-8, RG-11, RG-58 and RG-59. RG-58 and RG-8 are 50 ohm coaxes, unsuited for video work. RG-6, RG-59 and RG-11 are all 75 ohm cable types, with RG-59 being the smallest (20 AWG centre conductor), RG-6 in between (18 AWG), and RG-11 being the largest (14 AWG).
Wireless Transmitters and Receivers
When it is difficult to run a cable to transmit video signals of the camera to the monitor, you might want to consider wireless transmission. But, the wireless signals may be attenuated or blocked by heavy metal walls, high voltage power lines, microwave equipment and others.
Currently, the most commercialized wireless systems are;
a) 900Mhz Frequency with 300ft maximum transmission,
b) 2.4Ghz Frequency with 300ft maximum transmission, and c) 2.4Ghz Frequency with 700ft maximum transmission.
A 5.8 GHz Frequency with maximum 7 miles transmission distance is also commercialized but it is not yet widely used because of its high cost.
The wireless system is strictly controlled by the FCC. The commercialized models are usually FCC approved by the manufacturers and you don't need to get a separate FCC approval. But, you can not change or modify the specification of each model without prior approval from the FCC. Each manufacturer has different bandwidths of frequency approved from the FCC and will not be compatible with other manufacturer's models.
Most commercialized wireless systems have 4 channels; you can not use more than 4 transmitters in one area due to conflicts of the overlapped channel(s). But you can have as many additional wireless receivers as you want.
Some transmitters have a built-in camera. Others do not and are to be connected with external video cameras (or other video sources) to transmit the video (and audio) signals. Wireless receivers are available with manual 4 channels or with automatic sequential switcher built-in 4 channels. Wireless receivers are to be connected to CCTV monitor, VCR or standard TV by RCA connectors.
How the video signal is transmitted from the camera to the control point is usually determined by the most effective means available. Not all applications can use or should use the same method for transmitting the video image.
Coaxial cable
Coax is the most common method of transmitting the signal. It provides very high bandwidth and assures the transmission of high quality video within its distance parameters. It is restricted, primarily by distance and the quality of the cable used. Coaxial cable has proper electrical features to transmit the video signals from the camera to the monitor. Among various coaxial cables, RG59/U is most common with a 75-ohm impedance and can be installed up to 450ft distance without loosing the video quality. This cable is usually connected by BNC connectors at both ends.
Twisted pair
This method requires the use of a pair of twisted wires to carry the video image. Since the redevelopment and upgrade of twisted pair technology in the early 1990s, twisted pair transmission technology is fast outpacing coaxial cable.
Fiber Optics
Fiber is clearly the best method for transmitting video over longer distances. When using fiber, the video signal is electronically changed into pulsed light. This light is then injected to a fiber. At the other end of the fiber, the pulsed light is changed back into an electronic signal. The advantages of fiber are that the video signal can be sent over long distances without significant degradation. Fiber-Optic Cable is not affected by electrical interference and has no problem even in contact with high-voltage power. It transmits video signals with extremely high efficiency and can run up to miles. The problem is that it is expensive and difficult to handle.
RCA Cable
RCA cable is not standard in the industry but is used a lot, specially for short distances up to 250ft. Twisted wire from 14 to 24 AWG (American Wire Gauge) with RCA connections at both ends will work as RCA cable. Even though its transmission quality is not as good as Coaxial Cable or Fiber-Optic, RCA cable is widely used because it is very easy to handle and has no problem of loosing video signal up to 250ft distance.
DIN Cable
Most observation systems which are pre-assembled at the factory have DIN cables with DIN connectors at both ends. DIN cables have 5 or 6 wires inside the configuration of which is, for example; wire 1 is for video, wire 2 is for audio, wire 3 is for power(12VDC, positive), wire 4 and 5 are for speaker(positive and negative), wire 6 is for ground. Mini DIN cable, which is used for mini camera package, comes with 4 wires inside. DIN cable, large or mini, can run up to 250 ft distance without loosing the video quality
Microwave
This is the use of microwave radio waves to transmit the video signal across areas ranging from 200 meters (short range) to ten miles (long range). In the US, microwave systems over 100 mili- watts must be licensed by the FCC in advance of installation. Microwave systems must have an open line-of-sight between the transmitter and the receiver.
WAN Digital transmission
The introduction of the internet in the mid 1990’s opened the door for wide area control and monitoring systems within the CCTV industry. Used by large corporate entities, a single control point is now able to monitor activities at multiple points around the world. Wide area networks can be built using private network communications paths, or use the Internet as the communications medium. Major disadvantages of intranet transmission include bandwidth restrictions and potential interference or security breaches from hackers.
Cable Ties
Because the transmission of video signals is directly related to the spacing between the inner wires or conductor and shield, any changes in the distance between the wires or conductor and shield will degrade the picture quality. This change may be caused by tight bends, kinking, indentations, stapling or others. That's why you need to use suitable cable ties and cable management when working with Coaxial Cable or DIN cable.
What is RG?
RG stands for military specs Radio Guide (which is old and meaningless anymore) and the RG numbers are kind of arbitrary. The most common RG designations seen these days are RG-6, RG-8, RG-11, RG-58 and RG-59. RG-58 and RG-8 are 50 ohm coaxes, unsuited for video work. RG-6, RG-59 and RG-11 are all 75 ohm cable types, with RG-59 being the smallest (20 AWG centre conductor), RG-6 in between (18 AWG), and RG-11 being the largest (14 AWG).
Wireless Transmitters and Receivers
When it is difficult to run a cable to transmit video signals of the camera to the monitor, you might want to consider wireless transmission. But, the wireless signals may be attenuated or blocked by heavy metal walls, high voltage power lines, microwave equipment and others.
Currently, the most commercialized wireless systems are;
a) 900Mhz Frequency with 300ft maximum transmission,
b) 2.4Ghz Frequency with 300ft maximum transmission, and c) 2.4Ghz Frequency with 700ft maximum transmission.
A 5.8 GHz Frequency with maximum 7 miles transmission distance is also commercialized but it is not yet widely used because of its high cost.
The wireless system is strictly controlled by the FCC. The commercialized models are usually FCC approved by the manufacturers and you don't need to get a separate FCC approval. But, you can not change or modify the specification of each model without prior approval from the FCC. Each manufacturer has different bandwidths of frequency approved from the FCC and will not be compatible with other manufacturer's models.
Most commercialized wireless systems have 4 channels; you can not use more than 4 transmitters in one area due to conflicts of the overlapped channel(s). But you can have as many additional wireless receivers as you want.
Some transmitters have a built-in camera. Others do not and are to be connected with external video cameras (or other video sources) to transmit the video (and audio) signals. Wireless receivers are available with manual 4 channels or with automatic sequential switcher built-in 4 channels. Wireless receivers are to be connected to CCTV monitor, VCR or standard TV by RCA connectors.