In telecommunications a communications system is a collection of individual communications networks, transmission systems, relay stations, tributary stations and data terminal equipment (DTE) that are generally capable of interconnection and interoperation to form an integrated whole. The components of a communications system have a common purpose, are technically compatible, use common procedures, respond to controls and operate in conjunction. Telecommunications are a method of communication (for example, for the transmission of sports, media, journalism, etc.).
A communication channel simply refers to the medium through which a signal travels. There are two types of means by which electrical signals travel, that is, guided and unguided. The guided means refer to any means that can be directed from the transmitter to the receiver by means of connection cables. In fiber optic communication, the medium is an optical fiber (glass type). Other guided media may include coaxial cables, telephone cables, twisted pairs, etc. The other type of media, unguided means, refers to any communication channel that creates space between the transmitter and the receiver. For radio or RF communication, the medium is air. Air is the only thing between the transmitter and receiver for RF communication, while in other cases, such as sonar, the medium is usually water because sound waves travel efficiently through certain liquid media. Both types of media are considered unguided because there are no connection cables between the transmitter and the receiver. The communication channels include almost everything, from the vacuum of space to solid pieces of metal; however, some media are preferred more than others. This is because the different sources travel through subjective means with fluctuating efficiencies.