The ഏകാന്ത കേബിൾ uses hard copper wire as the core and a layer of insulating material. This layer of insulating material is surrounded by a densely woven mesh conductor, and the net is covered with a layer of protective material. There are two widely used ഏകാന്ത കേബിൾs. One is a 50-ohm cകഴിവുള്ള, which is used for digital transmission, and is also called baseband ഏകാന്ത കേബിൾ because it is mostly used for baseband transmission; the other is a 75-ohm cകഴിവുള്ള, which is used for analog transmission, which is the broadband ഏകാന്ത കേബിൾ to be discussed in the next section. This difference is caused by historical reasons, not technical reasons or manufacturers.
This structure of ഏകാന്ത കേബിൾ makes it have high bandwidth and excellent noise suppression characteristics. The bandwidth of a ഏകാന്ത കേബിൾ depends on the cകഴിവുള്ള length. A 1km cകഴിവുള്ള can reach a data transmission rate of 1Gb/s~2Gb/s. Longer cകഴിവുള്ളs can also be used, but the transmission rate should be reduced or intermediate amplifiers should be used. Currently, ഏകാന്ത കേബിൾs are largely replaced by optical fibers, but they are still widely used in cകഴിവുള്ള television and some local area networks.
A ഏകാന്ത കേബിൾ system that uses a limited TV cകഴിവുള്ള for analog signal transmission is called a broadband ഏകാന്ത കേബിൾ. The term "broadband" comes from the telephone industry and refers to a frequency band wider than 4kHz. However, in computer networks, "broadband cകഴിവുള്ള" refers to any cകഴിവുള്ള network that uses analog signals for transmission.
Because the broadband network uses standard cകഴിവുള്ള television technology, the usകഴിവുള്ള frequency band is up to 300MHz (often to 450MHz); due to the use of analog signals, an electronic device needs to be placed at the interface to convert the bit stream entering the network into an analog signal, and Convert the signal output from the network into a bit stream.
Broadband systems are divided into multiple channels, and TV broadcasting usually occupies 6MHz channels. Each channel can be used for analog TV, CD quality sound (1.4Mb/s) or 3Mb/s digital bit stream. TV and data can be mixed on a single cകഴിവുള്ള.
A major difference between a broadband system and a baseband system is that because the broadband system covers a wide area, it requires an analog amplifier to periodically strengthen the signal. These amplifiers can only transmit signals in one direction. Therefore, if there are amplifiers between computers, packet packets cannot be transmitted backwards between computers. To solve this problem, two types of broadband systems have been developed: dual-cകഴിവുള്ള systems and single-cകഴിവുള്ള systems.
A dual cകഴിവുള്ള system has two identical cകഴിവുള്ളs laid side by side. In order to transmit data, the computer transmits the data through the cകഴിവുള്ള 1 to a device at several roots of the cകഴിവുള്ള, that is, the head-end, and then the head-end transmits the signal down the cകഴിവുള്ള through the cകഴിവുള്ള 2. All computers send via cകഴിവുള്ള 1 and receive via cകഴിവുള്ള 2.
Another solution is to allocate different frequency bands for internal and external communications on each cകഴിവുള്ള. The low frequency band is used for communication from the computer to the top device, and the signal received by the top device is moved to the high frequency band and broadcast to the computer. In the subsplit system, the 5MHz~30MHz frequency band is used for inward communication, and the 40MHz~300MHz frequency band is used for outward communication. In the midsplit system, the inward frequency band is 5MHz~116MHz, and the outward frequency band is 168MHz~300MHz. This choice is caused by historical reasons.
A dedicated permanent channel can be allocated between a pair of computers; other computers can apply to establish a temporary channel through the control channel, and then switch to the applied channel frequency; and all computers can share one or a group of channels. Technically speaking, broadband cകഴിവുള്ളs are worse than baseband (single channel) cകഴിവുള്ളs in sending digital data, but its advantage is that it has been widely installed.