Shopping cheats: video cable precautions and problem solving

At present, the domestic security cable enterprises in the industry order continues to standardize, the market environment gradually healthy at the same time, through the continuous improvement of their own strength and the continuous extension of products and services, the security cable industry like China's security industry like a spring breeze, will definitely be vigorously developed, let us join hands to jointly push the security industry with brilliant prospects to deepen.

Cable purchase precautions

Video signal transmission generally adopts direct modulation technology, in the form of baseband frequency (about 8MHz bandwidth), and the most commonly used transmission medium is coaxial cable
.
Coaxial cable is specially designed to transmit video signals, and its frequency loss, image distortion, and image attenuation amplitude are relatively small, which can well complete the task
of transmitting video signals 。 Generally, special SYV75 ohm series coaxial cable is used, and the commonly used model is SYV75-5 (its non-relay transmission distance for video signals is generally 300-500m); When the distance is long, it is necessary to use SYV75-7, SYV75-9 or even SYV75-12 coaxial cable (in actual engineering, the transmission distance of thick cable without relay can reach more than 1km); There are also video amplifiers to enhance the brightness, chrominance and synchronization signal of the video, but the interference signal in the line will also be amplified, so too many video amplifiers can not be connected in series in the loop, otherwise saturation will occur, resulting in image distortion; Optical fiber transmission has a series of advantages such as small attenuation, frequency bandwidth, no electromagnetic interference, light weight, good confidentiality, etc.
, mainly used in national, provincial and municipal backbone communication networks, cable TV networks and high-speed broadband computer networks
.
In CCTV monitoring systems, optical fiber transmission has also become the preferred way
of long-distance video and audio and control signal transmission.

Video signals can also be transmitted over twisted pair, which requires twisted pair transmission equipment
.
In some special applications, twisted pair transmission equipment is indispensable
.
For example, when a large number of twisted pairs (called Category 3 or Category 5 wires in the standard) have been laid in the building according to the comprehensive wiring standard, and there are corresponding information interfaces (RJ45 or RJ11) in each related room, there is no need to rewire when adding CCTV monitoring equipment, and video and audio signals and control signals can be transmitted through twisted pairs, among which the transmission of video signals uses twisted pair transmission equipment
.
In addition, twisted pair transmission equipment is also required for applications that have been laid with twisted pair (or two-core sheathed wire) and need to transmit the image of the front-end camera to the central control room equipment
.
The function of twisted pair video transmission equipment is to convert the video signal suitable for unbalanced transmission (that is, suitable for 75 coaxial cable transmission) into a video signal suitable for balanced transmission (that is, suitable for twisted pair transmission) at the front end; At the receiving end, the opposite processing is performed on the front end, and the video signal transmitted through the twisted pair is reconverted into an unbalanced video signal
.
The twisted pair transmission device itself has a video amplification effect, so it is also suitable for long-distance signal transmission
.
For the above different transmission methods, the transmission components and transmission lines used are quite different
.

Communication cables are generally used in camera devices equipped with motorized gimbal and motorized lenses, and remote control decoders
need to be installed on site when used.
The communication transmission cable between the field decoder and the video matrix switching host of the control center generally adopts 2-core shielded communication cable (RVVP) or 3 types of twisted pair UTP, with a cross-sectional area of 0.
3mm2~0.
5mm2
per core.
The basic principle of choosing a communication cable is that the longer the distance, the larger
the wire diameter.
For example, the basic communication distance specified by RS-485 communication is 1200m, but the sheath line of RVV2-1.
5 can be used in actual engineering to extend the communication length to more than
2000m.
When the communication distance is too long, RS-485 communication repeaters
are used.

The control cable usually refers to the multi-core cable used to control the gimbal and the motorized variable lens, which is connected to the gimbal and motorized lens control terminal of the controller or decoder at one end, and the other end is directly connected to the corresponding terminal of the gimbal and motorized lens
.
Since the control cable provides DC or AC voltage, and the distance is generally short (sometimes less than 1m), there is basically no interference problem, so there is no need to use shielded wires
.
Most of the commonly used control cables use 6-core or 10-core cables, such as RVV6-0.
2, RVV10-0.
12, etc
.
Among them, the 6-core cable is connected to the 6 terminals of the gimbal, the top, bottom, left, right, automatic and public, and the 10-core cable includes the zoom, focus, aperture and common 4 terminals of the motorized lens in addition to the 6 terminals
of the gimbal.
In the CCTV monitoring system, the control cable from the decoder to the gimbal and the lens is generally not required due to the relatively short distance; The distance from the controller in the central control room to the gimbal and the electric lens is as little as tens of meters, and as much as hundreds of meters, and the control cable needs to have certain requirements, that is, the wire diameter should be thick, such as RVV10-0.
5, RVV10-0.
75, etc
.

Sound monitoring cables generally use 4-core shielded communication cable (RVVP) or Category 3 twisted pair UTP, with a cross-sectional area of 0.
5mm2
per core.
In the absence of interference environment, it can also be selected as unshielded twisted pair, such as Category 5 twisted pair (4 to 8 cores) commonly used in integrated wiring; Since the audio signal of the monitoring head in the monitoring system is transmitted to the central control room by point-to-point wiring method, with high voltage and small current transmission, it is enough to use unshielded 2-core cable, such as RVV2-0.
5
.

Cable purchase problem is solved

Q: Is the crimp end pipe directional?

A: For stepless (straight) tailpipes from BCP-C3B or comparable BNCs, the orientation of
the tailpipes is irrelevant when installed.
For BCP-C5FA or other tailpipes with a bevel (Cao line) at one end, the tailpipes are also non-directional when installed
.
However, for stepped tailpipes, such as those of BCP-C1, they are directional
.

Q: For coaxial cable with aluminum foil shielding, how should aluminum foil be handled?

A: If the aluminum foil is not firmly glued, all exposed aluminum foil should be peeled off
.
If the aluminum foil is attached to the insulator and stands firmly, please make sure that the conductor at the cutting end of the insulator and the debris of the aluminum foil can be cleaned up, because these debris may cause a short circuit
.

Q: Why do some other companies' connectors have a cutting-edge central contact pin? Do these BNC connectors match Canamy's BNC sockets?

A: BNCs with pointed central pins meet the JIS standard
of 50.
The central contact pin of the Canamy BNC complies with the military standard (MIL standard) and is therefore not pointed
.
The two different methods have no direct impact
on the quality of contact.
The actual contact surface of the Canamen BNC connector is consistent with the standard, so there are no compatibility issues
.

Q: For cables not listed in the connector matching cable table, can the same connector connection be used as long as the dimensions are close?

A: No
.
While the connection installation itself may be feasible, the quality of the connection can be severely affected
.
Although the connection seems to work, factors such as appliance stability, weak cable connection strength, and other factors can cause problems
in actual use.
Therefore, these cables that are not listed must be tested and evaluated to determine whether the connector
can be matched.
This issue should be paid special attention to
when using crimp type connectors.

Q: What is cable connection strength?

A: Cable connection strength refers to the maximum load
on a cable when it is pulled out of the connector by tensile stress.
For Canamy products, "cable connection strength" refers to the connection strength of the outer conductor of the cable, excluding the connection strength of the central contact pin and the inner conductor
.