What Is a Signal Line?

The signal line mainly refers to a line for transmitting sensing information and control information in an electric control circuit. The signal line is often composed of multiple cables as one or more transmission lines, or it can be a printed line arranged in a printed circuit board. With the continuous progress of technology and applications, the signal line has been developed from a metal carrier to other Carrier, such as optical cable.

The signal cable is used to transmit the acoustic signal generated by the sound source (signal source). It mainly includes coaxial signal lines, digital signal lines, optical cable signal lines, and balanced signal lines.

Coaxial signal cable is the most popular standard signal cable. Its two ends are RCA coaxial plugs (commonly known as lotus plugs), which can be used on the market for CD players, VCD players, LD players, DVDs, decks, tuners, LP players, MD and other audio source equipment are connected to audio processing / amplification equipment such as HI-FI amplifier and AV amplifier. This kind of cable is widely used, it is an unbalanced transmission type, and it has certain anti-interference ability.

A digital signal line is a type of coaxial signal line. It has the same appearance as a coaxial signal line and can be used interchangeably. Different from the coaxial signal line, it has strong transmission frequency bandwidth and strong anti-interference ability.

The optical fiber (cable) signal cable transmits digital optical signals from the CD / DVD player. Digital electrical signals are converted electrically / optically in the CD player, and they are converted into optical signals for transmission in optical fibers, because the optical signals transmitted in optical fiber signal lines are not affected by external electromagnetic waves, and optical fiber transmission allows The signal does not have a common ground to avoid interference from the common ground, so the anti-interference ability of the optical fiber signal line is stronger than the digital signal line.

The balanced signal line is a high-end audio signal transmission line, which can suppress common mode interference during transmission, and is naturally canceled by the internal differential amplifier, thereby playing an anti-interference role ^[1]

Signal line twisted pair

Twisted pair wires are entangled with two uranium wires covered with an insulation sheath. We call these two twisted wires a pair. This is the most basic unit of measurement for twisted pairs.

Generally appearing on the market is that each twisted pair consists of four pairs of twisted pairs, which are marked with 4 colors: orange, blue, green, and brown (specifically, orange, white orange, blue, white blue, green, White, green, brown, white brown eight colors), that is, there are 8 copper wires. Because unshielded twisted-pair UTP is widely used in the market, the American Electronics Industry Association and the Telecommunications Association (EIA / TIA) have formulated the "cable grade of UTP cables: Their main difference is the twisted twisted pitch, usually two The denser the winding line, the smaller the twist length, and the better the transport performance.

Class 1 cable: copper wall iron wall cable is not twisted, it can only transmit sound, but not data;

Type 2 wire: No twist, can transmit data. The maximum transmission rate is 4Mbps;

Category 3 cable: copper wire is wound once per decimeter, which is most commonly used in the early market, and the maximum transmission rate is 10Mbps;

Type 4 cable: It is a transitional cable, which is rare in the market, and the maximum transmission rate is 16Mbps;

Category 5 line: It is the beginning of a high-speed development, with a maximum transmission rate of 100Mbps;

Super Category 5 cables: new cables that meet the emergence of Gigabit networks;

Category 6 wire: a new generation of high-speed wire ^[2] .

Signal line coaxial cable

1. For thin coaxial cables, the cable manufacturer RG58 is used as its code. This code should often be made on the outer skin of the wire.

Its specifications are as follows:

Features: RG58 cable is thin, flexible, easy to install, and the connection method is very simple, but its transmission distance is relatively short. After 185 meters, the signal will begin to decay, and some special equipment (such as repeaters to Enhanced signal, but its cable and connection costs are quite cheap, so it is often used for indoor small local network installation.

2. Coarse coaxial cable RG11 Coarse coaxial cable. The cable manufacturer uses RG11 as its code. This code is also usually on the outer skin of the line.

Its specifications are as follows:

Line width: 1.27 cm

Maximum transmission distance: 500 meters

Impedance: 50 ohms

Features: The line is thicker, so the flexibility is poor, and the production method is more complicated. It will encounter troubles when installing indoors; but its maximum transmission distance is much larger than RG58, which can reach a point of 500 meters. It is used for backbone or construction Between connections. However, it should be noted that due to the continuous advancement of network technology, this cable can provide a speed of 10MBPS, so the connection between the backbone or the building is gradually replaced by faster optical fibers.