Common cable monitoring One-line monitoring equipment is specially developed for video surveillance. It uses reliable cable television network transmission technology to transmit video surveillance signals.
The common cable monitoring and monitoring system has many advantages such as strong anti-interference ability, long transmission distance, easy wiring, and low price. With the use of a common cable monitoring device, the multi-channel monitoring signal can be transmitted far to several kilometers or even farther away. Moreover, the quality of the transmitted image can be comparable to that of an optical transceiver, and the image quality can reach 4 or more levels. Its obvious advantages are:
1) The transmission distance is long and the transmission quality is high. Because advanced intermediate frequency processing and up-conversion technology are adopted in the common cable one-line transmitter, it is excellently compensated for the attenuation of the amplitude of the video signal by the high-frequency coaxial cable and between different frequencies. Attenuation difference maintains the brightness and color of the original image as well as real-time performance. When the transmission distance reaches several kilometers or more, the image signal is basically free of distortion. If the use of relay high-frequency amplification transmission distance will reach tens of kilometers.
2) Simple wiring and high cable utilization A coaxial cable can transmit more than 10 monitoring signals. The wiring combination is eclectic, and it can use bus, tree, star and many kinds of structures to integrate multi-point image and control into one cable bus to transmit bidirectionally.
The common cable monitoring and transmission system makes full use of the cable resource space, greatly simplifies the wiring structure, and greatly reduces the wiring costs and construction costs. Using this system, you can realize the convenience of using more than a hundred monitoring points to make use of a few lines of transmission. At the same time, the amount of maintenance and costs are also suddenly reduced.
3) Strong anti-jamming, applicable to wide-band high-frequency transmission mode can effectively suppress common mode interference and electromagnetic interference, even in the harsh environment of electromagnetic environment of large factories, power plants, coal mines, elevators and so on.
4) The expansion is simple, and the structure of the bus topology is upgraded smoothly. There is no need for separate cabling. When the camera points are temporarily added, only one set of common cable pass through equipment and tens of meters of wire need to be added. No re-wiring is required, which involves huge construction costs. Spending time and adding it to the main line nearby is completed. For example, a 20-channel surveillance system originally needed to add 3 video cameras at the time of surveillance. The traditional approach requires at least three or five days of re-wiring of the casing. Moreover, it takes time to consume power, and the use of the common-cable equipment is only In the nearest location, inserting a short line into the trunk can send the newly added image to the control room. It can be completed in half an hour.
1) Equipment composition: transmitter + receiver 2) media composition: SYWV-75 series wire 3) accessories: mixer, distributor, F head, TV head 4) measuring tool: field strength meter ( Simple type)
1) Equipment composition: Transmitter + receiver transmitter is usually located near the camera. The image signal captured by the camera is transmitted to the transmitter through a small video cable. The transmitter internal conversion circuit modulates the image source to different frequencies. The high-frequency carrier is transmitted to the corresponding band of the RF cable for transmission.
Note: The available bandwidth of the coaxial cable is 0~1000MHz, and the traditional monitoring signal only occupies 0~6MHz, while the cable TV uses the frequency from 45MHz later. The bandwidth of each channel has 8MHz (including the image With sound, so a cable can theoretically transmit more than 100 audio and video images.
The common cable one-way pass is exactly the audio and video transmission of the analog cable TV. The transmitter adopts the I2C bus structure, the fixed-frequency SAW filter (custom), the fixed-frequency resonator (custom) and other components to modulate the image signal to the frequency after 45MHz. Each adjacent 8MHz is a channel. When multiple images are transmitted on the same cable, each image is encoded into a different frequency signal by using different frequency transmitters. Different channels are used to achieve mutual non-overlapping. Parallel transmission in the affected state.
The receiver is a device installed in the control room. The role of the receiver is to restore the radio frequency signals of different channels transmitted from the front-end transmitter to an image signal and output it to a display device, a video recording device, and the like.
The main component of the receiver's image restoration is the imported high-frequency head. This is a picture element that the world recognizes as the most effective and stable to receive the standard RF signal. Through the I2C bus control, intelligent frequency locking and other methods to achieve FM restore audio signal.
According to CATV's classification of image quality, we need to set the required level strength to 65 dB when accessing the high-frequency head when we want to achieve a level 4 or higher image standard.
The receiver is divided into single-channel type and multi-channel type. The single-channel receiver can only restore one channel of video signal at the same time, but it can restore the transmitter image of any channel on the front-end. The multi-channel receiver can also recover multiple video signals at the same time. For example, an 8-channel receiver can simultaneously restore 8 channels of video signals.
2) Medium composition: SYWV-75 series wire A. The transmission medium used by the common cable is SYWV-75 series RF cable (commonly known as cable TV line).
Note: The SYV-75 series is a popular video cable (closed-circuit television line). The efficiency of transmitting RF signals is about 80% of SYWV-75, that is, if a channel can transmit 100 meters distance on the SYWV-75 RF line, On the SYV-75 line, it can only transfer about 80 meters.
B. The core type is a single stranded copper axis core, that is, the centerline core is a thick copper axis (the transmission effect of multiple strands is only 1/3 of a single strand, not recommended).
C. Shielded nets use copper tin-plated nets (better than aluminum-plated copper nets), and the more the number is compiled, the better it is to block external disturbances, which are generally more than 64 series.
D. The thickness of the line type is mainly considered from the transmission distance, for example within 500 meters, SYWV-75-5 can be used as the main line, 500-1000 meters, use SYWV-75-7 as the main line, more than 1000 meters, use SYWV-75-9 as Main line.
3) Accessories: Mixer, distributor, F head, TV head multi-channel RF signal to be mixed, in principle, it is necessary to join the mixer, but the number of mixers is generally more than 16 ways, and the cost is very high (usually a thousand dollars), but the cable structure of the common cable, there are rarely 16 images mixed together, so the use of mixer is not realistic. The actual use of the distributor is often reversed to use as a mixer, that is, the distributor OUT port as an input, IN as an output.
The principle difference between the distributor reverse connection and the mixer is that: the mixer uses the principle of directional coupler, the isolation between the ports is very high, and the isolation of the distributors is not high, and the RF signal is less The small system can still be used. (Note: There are some two-way, four-way mixers on the market. Selling prices are around RMB 20, all of which are copycat products. Basically, they act as distributors and beware of scams.)
The F head is a dedicated connector for RF signals. The principle of skin effect means that when the F head is manufactured, the protruding part of the copper shaft should be kept smooth, and it can be in complete contact with the shrapnel in the F seat (note that some wires have a transparent outer layer in the copper shaft. The rubber sleeve, resulting in poor contact, level attenuation is too large), In addition, F head, F seat has metric, imperial two systems, must be used in conjunction, Zhang Guan Li Dai, but also easily lead to signal weakening.
The TV head is used for connecting high-frequency heads. It is generally used on single-channel receivers and is simple to produce.
4) Measurement Tool: Field Strength Meter (Simple)
The full-featured field strength meter is a device that can measure a variety of parameters. As a common cable, only the level strength is required for the first-line debugging. Therefore, we recommend using a simple field strength meter.
The unit of level intensity is dB and the range of values ​​is: 30-120. When the signal is lower than 30DB, the symbol "-" indicates that the signal is extremely weak and cannot be mapped.
It is necessary to use the field strength meter. When a line is connected properly, as long as the field strength meter is connected to any point on the trunk line and the channel selection is pressed up or down, channels existing on the trunk line can be detected. If the 01 channel is installed in the system, the field strength meter cannot measure the level of the channel, indicating that the 01 channel is not normal when it is connected to the main line, and it is certainly a bad connection in a certain connected place; or If the channel signal is too weak, it can be determined that there is a problem with the connection somewhere.
The common cable monitoring and monitoring system has many advantages such as strong anti-interference ability, long transmission distance, easy wiring, and low price. With the use of a common cable monitoring device, the multi-channel monitoring signal can be transmitted far to several kilometers or even farther away. Moreover, the quality of the transmitted image can be comparable to that of an optical transceiver, and the image quality can reach 4 or more levels. Its obvious advantages are:
1) The transmission distance is long and the transmission quality is high. Because advanced intermediate frequency processing and up-conversion technology are adopted in the common cable one-line transmitter, it is excellently compensated for the attenuation of the amplitude of the video signal by the high-frequency coaxial cable and between different frequencies. Attenuation difference maintains the brightness and color of the original image as well as real-time performance. When the transmission distance reaches several kilometers or more, the image signal is basically free of distortion. If the use of relay high-frequency amplification transmission distance will reach tens of kilometers.
2) Simple wiring and high cable utilization A coaxial cable can transmit more than 10 monitoring signals. The wiring combination is eclectic, and it can use bus, tree, star and many kinds of structures to integrate multi-point image and control into one cable bus to transmit bidirectionally.
The common cable monitoring and transmission system makes full use of the cable resource space, greatly simplifies the wiring structure, and greatly reduces the wiring costs and construction costs. Using this system, you can realize the convenience of using more than a hundred monitoring points to make use of a few lines of transmission. At the same time, the amount of maintenance and costs are also suddenly reduced.
3) Strong anti-jamming, applicable to wide-band high-frequency transmission mode can effectively suppress common mode interference and electromagnetic interference, even in the harsh environment of electromagnetic environment of large factories, power plants, coal mines, elevators and so on.
4) The expansion is simple, and the structure of the bus topology is upgraded smoothly. There is no need for separate cabling. When the camera points are temporarily added, only one set of common cable pass through equipment and tens of meters of wire need to be added. No re-wiring is required, which involves huge construction costs. Spending time and adding it to the main line nearby is completed. For example, a 20-channel surveillance system originally needed to add 3 video cameras at the time of surveillance. The traditional approach requires at least three or five days of re-wiring of the casing. Moreover, it takes time to consume power, and the use of the common-cable equipment is only In the nearest location, inserting a short line into the trunk can send the newly added image to the control room. It can be completed in half an hour.
1) Equipment composition: transmitter + receiver 2) media composition: SYWV-75 series wire 3) accessories: mixer, distributor, F head, TV head 4) measuring tool: field strength meter ( Simple type)
1) Equipment composition: Transmitter + receiver transmitter is usually located near the camera. The image signal captured by the camera is transmitted to the transmitter through a small video cable. The transmitter internal conversion circuit modulates the image source to different frequencies. The high-frequency carrier is transmitted to the corresponding band of the RF cable for transmission.
Note: The available bandwidth of the coaxial cable is 0~1000MHz, and the traditional monitoring signal only occupies 0~6MHz, while the cable TV uses the frequency from 45MHz later. The bandwidth of each channel has 8MHz (including the image With sound, so a cable can theoretically transmit more than 100 audio and video images.
The common cable one-way pass is exactly the audio and video transmission of the analog cable TV. The transmitter adopts the I2C bus structure, the fixed-frequency SAW filter (custom), the fixed-frequency resonator (custom) and other components to modulate the image signal to the frequency after 45MHz. Each adjacent 8MHz is a channel. When multiple images are transmitted on the same cable, each image is encoded into a different frequency signal by using different frequency transmitters. Different channels are used to achieve mutual non-overlapping. Parallel transmission in the affected state.
The receiver is a device installed in the control room. The role of the receiver is to restore the radio frequency signals of different channels transmitted from the front-end transmitter to an image signal and output it to a display device, a video recording device, and the like.
The main component of the receiver's image restoration is the imported high-frequency head. This is a picture element that the world recognizes as the most effective and stable to receive the standard RF signal. Through the I2C bus control, intelligent frequency locking and other methods to achieve FM restore audio signal.
According to CATV's classification of image quality, we need to set the required level strength to 65 dB when accessing the high-frequency head when we want to achieve a level 4 or higher image standard.
The receiver is divided into single-channel type and multi-channel type. The single-channel receiver can only restore one channel of video signal at the same time, but it can restore the transmitter image of any channel on the front-end. The multi-channel receiver can also recover multiple video signals at the same time. For example, an 8-channel receiver can simultaneously restore 8 channels of video signals.
2) Medium composition: SYWV-75 series wire A. The transmission medium used by the common cable is SYWV-75 series RF cable (commonly known as cable TV line).
Note: The SYV-75 series is a popular video cable (closed-circuit television line). The efficiency of transmitting RF signals is about 80% of SYWV-75, that is, if a channel can transmit 100 meters distance on the SYWV-75 RF line, On the SYV-75 line, it can only transfer about 80 meters.
B. The core type is a single stranded copper axis core, that is, the centerline core is a thick copper axis (the transmission effect of multiple strands is only 1/3 of a single strand, not recommended).
C. Shielded nets use copper tin-plated nets (better than aluminum-plated copper nets), and the more the number is compiled, the better it is to block external disturbances, which are generally more than 64 series.
D. The thickness of the line type is mainly considered from the transmission distance, for example within 500 meters, SYWV-75-5 can be used as the main line, 500-1000 meters, use SYWV-75-7 as the main line, more than 1000 meters, use SYWV-75-9 as Main line.
3) Accessories: Mixer, distributor, F head, TV head multi-channel RF signal to be mixed, in principle, it is necessary to join the mixer, but the number of mixers is generally more than 16 ways, and the cost is very high (usually a thousand dollars), but the cable structure of the common cable, there are rarely 16 images mixed together, so the use of mixer is not realistic. The actual use of the distributor is often reversed to use as a mixer, that is, the distributor OUT port as an input, IN as an output.
The principle difference between the distributor reverse connection and the mixer is that: the mixer uses the principle of directional coupler, the isolation between the ports is very high, and the isolation of the distributors is not high, and the RF signal is less The small system can still be used. (Note: There are some two-way, four-way mixers on the market. Selling prices are around RMB 20, all of which are copycat products. Basically, they act as distributors and beware of scams.)
The F head is a dedicated connector for RF signals. The principle of skin effect means that when the F head is manufactured, the protruding part of the copper shaft should be kept smooth, and it can be in complete contact with the shrapnel in the F seat (note that some wires have a transparent outer layer in the copper shaft. The rubber sleeve, resulting in poor contact, level attenuation is too large), In addition, F head, F seat has metric, imperial two systems, must be used in conjunction, Zhang Guan Li Dai, but also easily lead to signal weakening.
The TV head is used for connecting high-frequency heads. It is generally used on single-channel receivers and is simple to produce.
4) Measurement Tool: Field Strength Meter (Simple)
The full-featured field strength meter is a device that can measure a variety of parameters. As a common cable, only the level strength is required for the first-line debugging. Therefore, we recommend using a simple field strength meter.
The unit of level intensity is dB and the range of values ​​is: 30-120. When the signal is lower than 30DB, the symbol "-" indicates that the signal is extremely weak and cannot be mapped.
It is necessary to use the field strength meter. When a line is connected properly, as long as the field strength meter is connected to any point on the trunk line and the channel selection is pressed up or down, channels existing on the trunk line can be detected. If the 01 channel is installed in the system, the field strength meter cannot measure the level of the channel, indicating that the 01 channel is not normal when it is connected to the main line, and it is certainly a bad connection in a certain connected place; or If the channel signal is too weak, it can be determined that there is a problem with the connection somewhere.
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