V: Polyvinyl chloride insulation.

V: Polyvinyl chloride insulation

V: Polyvinyl chloride sheath

B: Flat type.

S: SPT(Twisted pair type). 

A: Tin or silver plated.

F: High temperature resistant

P: Braided shielding 

P2: Copper tape shielding

P22: Steel tape armored 

Y: Prefabricated type, generally omitted, or polyolefin sheath

FD: Product category code, indicating branch cable.The forthcoming construction department standard is represented by FZ, which is essentially the same

YJ: Cross-linked polyethylene insulation

V: Polyvinyl chloride insulation or sheath

ZR: Flame retardant type 

NH: Fire-resistant type 

WDZ: Halogen-free low smoke flame retardant type

WDN: Halogen-free low smoke fire-resistant typ

II. Cable knowledge: Cables are usually divided into power cables and control cables.

1.The meaning of the common symbols of the cable:

(1) ZR: Flame retardant, NH: Fire-resistant, ZA(IA): Intrinsically safe

(2)Purpose: Power cable default representation, K: Control cable, P: Signal cable, DJ: Computer cable

(3)Insulation layer: V: Polyvinyl chloride, Y: Polyethylene, YJ: Cross-linked polyethylene, X: Rubber, Z: Paper

(4)Conductor: T: Copper core default representation, L: Aluminum core.

(5)Inner protective layer (sheath), V: Polyvinyl chloride, Y: Polyethylene, Q: Lead package, L: Aluminum package, H: Rubber, HF: Non-flammable rubber, LW: Wrinkled aluminum sheath, F: Neoprene, N: Butyl rubber sheath.

(6)Features: The package type does not need to be represented, F: Phase lead package phase sheath, D: No oil dripping, CY: Oil filling, P: Shielding, C: Dust filter, Z: Direct current

(7)Armored layer. 0: None, 2: Double steel belt (24: Steel belt, coarse round steel wire), 3: Fine round steel wire, 4: Coarse round steel wire (44: Double coarse round steel wire).

(8)Outer layer. 0: None, 1: Fiber layer, 2: Polyvinyl chloride sheath, 3: Polyethylene sheath.

(9)Rated voltage. Represented by numbers, kV.

2.Examples of commonly used cables: VV

Copper core polyvinyl chloride insulated polyvinyl chloride sheathed power cable. VV22 copper core polyvinyl chloride insulated polyvinyl chloride armored sheathed power cable. YJV cross-linked polyethylene insulated, polyvinyl chloride sheathed power cable.III.The meaning of the specification representation method The specification adopts the number of cores, nominal cross-section and voltage level representation

① Single-core branch cable specification representation method:

The number of cables in the same circuit*(1nominal cross-section), 0.6/1KV, such as: 4(1185)+1950.6/1KV

如:4*185+1*950.6/1KV 如：4*185+1*950.6/1KV

② Multi-core twisted branch cable specification representation method: The number of cables in the same circuitnominal cross-section, 0.6/1KV, Such as: 4185+1*950.6/1KV

③ Multi-core same sheath type branch cable specification representation method: Cable core number×nominal cross-section-T, such as: 4×25-T

Complete model specification representation method

Because the branch cable includes the trunk cable and the branch cable, and the two have different specifications and structures, there are two representation methods:

① The trunk cable and the branch cable are represented separately, such as: Trunk cable: FD-YJV-4*(1185)+1950.6/1KV Branch cable: FD-YJV-4*(125)+1160.6/1KV This method is particularly clear in design, and can conveniently represent different specifications of branch lines

② The trunk cable and the branch cable are represented together, such as: FD-YJV-4*(1185/25)+195/160.6/1KV This method is more intuitive, but it is limited to the case where the branch cable is of the same specification, and cannot represent different specifications of the branch line: Since the branch cable is mainly used for 1KV low-voltage distribution system, its rated voltage 0.6/1KV can be omitted in the design notation

5.Five-core cable, wire diameter calculation tips:

4 phase, ground wire is 2 times the 1 protective ground wire.

Such as: 4185+195, 185/2=92.5 take 95.495+150, 95/2=47.5 take 50450+125, 50/2=25 take 25 supplementary knowledge: single-core cable wire diameter specification 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400 unit: MM26

IV. Wire knowledge:

The common symbol meaning of the wire:

1.SYWV(Y), SYKV dedicated to cable television, broadband network Cable structure: (coaxial cable) single oxygen-free round copper wire + physical foamed polyethylene (insulation) + (tin wire + aluminum) + polyvinyl chloride (polyethylene)

2.Signal control cable (RVV sheath line, RVVP shielded line)

Suitable for building intercom, anti-theft alarm, fire protection, automatic meter reading and other projects.

3.RVVP copper core polyvinyl chloride insulated shielded polyvinyl chloride sheathed flexible cable voltage 300V/300V2-24 core

Use: Instrument, intercom, monitoring, control installation

4.KVVP: Polyvinyl chloride sheathed braided shielded cable

Use: Electrical appliances, instruments, power distribution device signal transmission, control, measurement

5.RVV (227IEC52/53) polyvinyl chloride insulated flexible cable

Use: Household appliances, small power tools, instruments, power lighting

6.RV polyvinyl chloride insulated cable

7.RVS, RVB suitable for household appliances, small power tools, instruments, power lighting connection cable

8.BV, BVR polyvinyl chloride insulated cable

Use: Suitable for electrical instrument equipment and power lighting fixed wiring

9.KVV polyvinyl chloride insulated control cable

Use: Electrical appliances, instruments, power distribution device signal transmission, control, measurement

10.RVV and KVV, RVVP and KVVP

Difference: RVV and RVVP use multi-strand fine copper wire composed of soft wire, namely RV wire.

11.KVV and KVVP use single-strand thick copper wire composed of hard wire, namely BV wire.

12.AVVR and RVVP difference: The same thing, only the internal cross-section is less than 0.75 square millimeters called AVVR greater than or equal to 0.75 square millimeters called RVVP.

13.SYV and SYWV difference: SYV is video transmission line with polyethylene insulation. SYWV is RF transmission line, physical foaming insulation. Used for cable TV.

14.RVS and RVV 2 core difference: RVS is a double-core RV line twisted together, without outer sheath, used for broadcast connection. RVV2 core line straight into the cable, with outer sheath, used for power supply, control signal and other aspects

V. Video transmission material knowledge (such as:CCTV cable ):

1.Classification of coaxial cables: Coaxial cables for video signal transmission .

There are SYV75-3, SYV75-5, SYV75-7, SYV75-9, SYV75-12

2.The meaning of each letter: SYV75-5-1(A, B, C) SYV75-5-41(A, B, C) SYV75-5-2(A, B, C) S represents RF coaxial cable Y represents polyethylene (PE) insulation V represents polyvinyl chloride (PVC) sheath 75 represents characteristic impedance 75 ohm 5 represents the approximate value of the outer diameter of the insulation -1,-41 or -2 represents the structure code. Generally -1 or -41 represents the inner conductor as a single core; -2 represents the inner conductor as a multi-core A: 64 weave B: 96 weave C: 128 weave 

VI. Network Cable Knowledge:

1.Classification of network cables: Twisted pair cables are usually divided into:

Currently, Category 5, Category 5e or Category 6 unshielded twisted pair cables are common in general local area networks, especially the current Category 5e and Category 6 unshielded twisted pair cables can easily provide 155Mbps communication bandwidth, and have the potential to upgrade to gigabit bandwidth, therefore, it has become the preferred cable for horizontal cabling today.

Twisted pair cables can also be divided into: shielded twisted pair cables and unshielded twisted pair cables. Most local area networks use unshielded twisted pair cables (UTP—Unshielded Twisted Pair) as the transmission medium for cabling to form a network. The network cable is composed of a certain length of twisted pair and an RJ45 head (crystal head).

2.Representation method of network cable: The identification of Category 5 cable is “cat5”, the identification of Category 5e cable is “cat5e”, the identification of Category 6 cable is “cat6”, the identification of Category 6a cable is “catA”, and the identification of Category 7 network cable is “cat7”.

Standard practice of crystal head:

568A standard: white green, green, white orange, blue, white blue, orange, white brown, brown

568B standard: white orange, orange, white green, blue, white blue, green, white brown, brown

General principles of practice:

Homogeneous (the two ends of the connection line are the same device) cross (make crossover line)

Heterogeneous (the two ends of the connection line are different devices) parallel (make parallel line)

The practice of crossover line is: one end adopts 568A standard, the other end adopts 568B standard

The practice of parallel line is: both ends adopt the same standard (both are 568A standard or 568B standard)

Note: When making a crystal head, make the crystal head’s reed face outward, the wire entry port face down, from left to right, follow the above line sequence, fully insert the wire (the copper core of the twisted pair can be seen at the top of the crystal head as the standard), and then use the network cable pliers to clamp it.

3.Introduction to the hub [commonly called “hub” (HUB)]:

(1) Introduction: The English name of the hub is “Hub”

“Hub” means “center”. The main function of the hub is to regenerate, reshape and amplify the received signals to expand the transmission distance of the network, and to concentrate all nodes on the nodes centered on it. It works on the first layer of the OSI (Open Systems Interconnection Reference Model), namely the “physical layer”. The hub, like network cards, network cables and other transmission media, is a basic device in the local area network and uses CSMA/CD (a detection protocol) access method.

(2) The difference between the hub and the switch: The hub is a pure hardware network bottom layer device, basically does not have the “intelligent memory” ability and “learning” ability similar to the switch. It also does not have the MAC address table of the switch, so when it sends data, it is not targeted, but is sent by broadcasting. That is to say, when it wants to send data to a certain node, it does not directly send the data to the destination node, but sends the data packet to all nodes connected to the hub.

4.This broadcast data sending method has two shortcomings:

(1) User data packets are sent to all nodes, which may bring about data communication insecurity. Some people with ulterior motives can easily illegally intercept other people’s data packets;

(2) Since all data packets are sent to all nodes at the same time, coupled with the shared bandwidth method introduced above, it is more likely to cause network congestion and further reduce network execution efficiency.

(3) Non-duplex transmission, low network communication efficiency. At the same time, each port of the hub can only carry out data communication in one direction, and cannot carry out two-way duplex transmission like a switch, the network execution efficiency is low, and it cannot meet the communication needs of larger networks. Despite this, the hub is still a bit tempting economically for homes or small businesses, especially suitable for networks with a few machines at home or as a branch network in small and medium-sized companies. HUB can be divided into passive HUB, active HUB, intelligent HUB according to the way of processing input signals.