What is a Cable Release?

Leakage cables are also commonly known as leakage induction cables. They are an outdoor perimeter intrusion detection system. They are mainly used in banks, vaults, high-end residences, prisons, warehouses, museums, power stations (including nuclear power stations), military institutions and facilities, bases, and oil fields , Cultural relics protection and other alarm places that need outdoor perimeter protection, can also be used as indoor various protection alarms.

Radial type: The outer conductor of the cable is opened at equal intervals in advance, and the interval between the openings is approximately equal to 1/2 of the working frequency wavelength, and the direction of signal radiation is perpendicular to the axis of the cable, which makes the coupling loss stable in a certain frequency band. 2200MHz band.

Coupling type: The same opening or slot is serially formed on the medium of the low-loss cable and the outer conductor. It has good performance in the GSM and DCS frequency bands and is specially used for indoor coverage systems.

(1) Coupling loss is the loss between the signal leaving the cable and the receiving antenna in the external space. Generally, the distance loss between 2 meters and the cable shall prevail. The above index is the coupling loss measured with 50% coverage probability.

(2) There are two types of coupling leakage cables. One type has small coupling loss and large line loss, and the other type has large coupling loss and small line loss. They can be selected according to different situations. ^[1]

(1)

The communication between the base station and the mobile station usually depends on radio transmission. At present, the continuous development of the communication industry increasingly requires that the base station and the mobile station can be connected at any time and anywhere, but in some special building environments. For example (tunnel), the electromagnetic wave propagation effect for mobile communication is not good. Antenna transmission in tunnels is also often difficult, so research on leaky cables has emerged as the times require.

LeakyCoaxialCable is also commonly referred to as leaky cable or leaky cable. Its structure is basically the same as that of ordinary coaxial cable. It consists of an inner conductor, an insulating medium, and an outer conductor with a periodic slot L. The electromagnetic wave is transmitted longitudinally in the leaking cable while radiating electromagnetic waves to the outside through the slot; the external electromagnetic field can also be induced into the leaking cable through the slot and transmitted to the receiving end. It can be said that the leaky coaxial cable has the functions of both a transmission line and a transmitting and receiving antenna.

At present, the frequency band of leaked cables covers more than 450MHz to 2GHz, which is suitable for various existing wireless communication systems. Applications include subways, railway tunnels, and highway tunnels with limited wireless transmission. In foreign countries, leaked cables are also used for indoor coverage. .

(1) The boundary of the coverage area of the three-dimensional prevention area is obvious, and the dead-end prevention can be achieved.

(2) The simple installation method is suitable for complex terrain installation, and can surround the boundary area of any shape. The leakage sensing cable can be buried underground or installed in the wall.

(3) With the function of preventing pets from false alarms, it can filter the interference of small animals, such as puppies and kittens moving in the defense area, to prevent false alarms and false alarms.

(4) Perfect adaptability is not affected by changes in ambient temperature, humidity, wind and rain, dust and trees.

(5) Detailed and extensive sensitivity adjustment function The four-speed sensitivity can be continuously adjusted, and the alarm threshold can be arbitrarily set according to environmental changes.

(6) Reasonable humanized structure design The shell adopts German advanced waterproof technology and integrated design of internal modules ^[2]

(1) Transmission loss: similar to the transmission loss of ordinary coaxial RF cables, that is, the signal gradually decays with the distance along the cable.

Degree in dB / 100m or dB / km.

(2) Coupling loss: The degree of attenuation of the signal when it radiates through the cable's outer conductor slot and propagates along the longitudinal direction of the cable (the signal attenuation value at 2m from the cable along the longitudinal direction of the cable, generally with a 95% probability of the signal attenuation As the basis for calculation of link budget), the unit is dB ^[3]

(1) The two cables should not cross each other and be installed close to each other, and the excess cables should be cut off; (including non-leaking cables)

(2) The two cables must be laid in parallel, with a spacing of 1-3 meters, and the optimal distance is 1.5 meters;

(3) The cable placement attempt is determined according to the medium. Generally, the buried depth of mud soil is 10-20 cm, and the buried depth of cement ground is 3-7 cm;

(4) The plane drop when two cables are laid in parallel is not less than 135 degrees;

(5) When installing two sets of cables, ensure that there is an overlap area of about 3 meters between the head and tail of two sets of adjacent leaking cables, and maintain a distance of about 0.3 meters between the two sets of cables in the overlap area. At the same time, the working frequencies of the hosts of two sets of leaking cables adjacent to each other should be staggered;

(6) When the host is installed outdoors, a waterproof protective box must be added to the host;

(7) The power line and signal line cannot be installed in parallel with the leaking cable. The distance between the signal line and the leaking cable should be greater than 30 cm, and the distance between the 220V power line and the leaking cable should be 1 meter away;

(8) The standard length of the non-leakage cable connecting the host and the leaky cable is 10 meters. The two non-leakage cables should be protected by pipes, which can be PVC pipes or steel pipes. The distance between the two non-leakages is more than 10 cm;

(9) The two leaking cables shall be installed in a 32MM PVC pipe and then buried in the ground, and shall not penetrate into the steel pipe;

(10) The buried position of the leakage cable should be more than 2 meters from the sidewalk and more than 4 meters from the highway;

(11) If the leaking cable is buried on one side of the wall, it must be 1 meter away from the wall.