Telecommunication channels, also called communications lines or links make use of the variety of telecommunications media for transmission of data over a telecommunication network. Generally, it is considered as bits per second, which is true in most of the cases. But in actual it is the number of times per second that the signal being transmitted, modulates or demodulates. These channels may be categorized into three broad categories.
- Wire cable (Coaxial cables and twisted pairs).
- Fiber optic cables.
- Microwave system. (electromagnetic).
This is the most common type of Telecommunication channels, used extensively throughout the world for communication purposes. It has two main types.
Twisted pair cables refer to the lines of telephone and telegraph. This channel is being used since long and most of the world telecommunication setup is based on this wire cable. It Television cable is the example of coaxial cable. This channel allows high-speed data transmission up to 50 million bits per second.
One of the most reliable and sophisticated telecommunication channel that transmits data up to several billion bits per seconds. This is about 15 times faster than the coaxial cable. Fiber optic used hair-thin filaments of glass and works on light pulses generated by a laser.
It can carry voice, data, and video with much more reliability than the other channels. They are better in terms of size and weight as well, a half-inch diameter fiber optic a carry up to 60,000 channels, compared to about 6,000 channels in a coaxial cable.
These systems have not wire connections. So the transmission has low error rate making it reliable, but expensive. As there is no wire connection, so it can be used for large area transmission. The system transmits a signal to a line of sight part between relay stations, approximately at a distance of 30 miles to boost up the signal. Satellites are also used in microwave communication.
Communication satellites are an important medium used in microwave communications. There are hundreds of communications satellites today in parking orbit (more than 400). Initially used for voice and video transmission, but now also used in large volume high-speed data transmission.
Communication Channel Bandwidth:
If the channel is considered as the highway, then the band width is like the number of lanes on that highway. More lanes more traffic at a time and high-speed transportation. There are three bands for communication channels:
- Narrow-band channel or the low-speed channel is he slowest band, transmits data from 40 bit per second to 1,200 bits per second. Telegraph lines are the example of narrow band channels.
- Voice band channel or the medium speed channel is faster than narrow band channels and transmits data from 110 bits per second to 9,600 bits per second. The telephone line is the example of voice and channels.
- Broad band channel or the high-speed channel is the fastest channel which transmits data up to several million bits per second and in special cases, goes up to billions of bits per second. Coaxial cable, Fiber optics, and Microwave are the examples of broad band channels.