Baird's device relied upon the Nipkow disk and thus became known as the mechanical television. It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning 30 September The first version of such a television to show promise was produced by Philo Farnsworth and demonstrated to his family on 7 September The development of transistor technology has been fundamental to modern electronic telecommunication. According Edholm's law , the bandwidth of telecommunication networks has been doubling every 18 months.
However, already in the s, researchers started to investigate packet switching , a technology that sends a message in portions to its destination asynchronously without passing it through a centralized mainframe. While Internet development was a focus of the Internet Engineering Task Force IETF who published a series of Request for Comment documents, other networking advancements occurred in industrial laboratories , such as the local area network LAN developments of Ethernet and the token ring protocol [ citation needed ].
The wireless revolution began in the s,    with the advent of digital wireless networks leading to a social revolution, and a paradigm shift from wired to wireless technology,  including the proliferation of commercial wireless technologies such as cell phones , mobile telephony , pagers , wireless computer networks ,  cellular networks , the wireless Internet , and laptop and handheld computers with wireless connections.
Realization and demonstration, on 29 October , of the first digital cinema transmission by satellite in Europe    of a feature film by Bernard Pauchon,  Alain Lorentz, Raymond Melwig  and Philippe Binant. Modern telecommunication is founded on a series of key concepts that experienced progressive development and refinement in a period of well over a century. Telecommunication technologies may primarily be divided into wired and wireless methods.
Overall though, a basic telecommunication system consists of three main parts that are always present in some form or another:. For example, in a radio broadcasting station the station's large power amplifier is the transmitter; and the broadcasting antenna is the interface between the power amplifier and the "free space channel". The free space channel is the transmission medium; and the receiver's antenna is the interface between the free space channel and the receiver.
Next, the radio receiver is the destination of the radio signal, and this is where it is converted from electricity to sound for people to listen to. Sometimes, telecommunication systems are "duplex" two-way systems with a single box of electronics working as both the transmitter and a receiver, or a transceiver. For example, a cellular telephone is a transceiver. This can be readily explained by the fact that radio transmitters contain power amplifiers that operate with electrical powers measured in watts or kilowatts , but radio receivers deal with radio powers that are measured in the microwatts or nanowatts.
Hence, transceivers have to be carefully designed and built to isolate their high-power circuitry and their low-power circuitry from each other, as to not cause interference. Telecommunication over fixed lines is called point-to-point communication because it is between one transmitter and one receiver. Telecommunication through radio broadcasts is called broadcast communication because it is between one powerful transmitter and numerous low-power but sensitive radio receivers. Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and to share the same physical channel are called multiplex systems.
The sharing of physical channels using multiplexing often gives very large reductions in costs. Multiplexed systems are laid out in telecommunication networks, and the multiplexed signals are switched at nodes through to the correct destination terminal receiver. Communications signals can be sent either by analog signals or digital signals. There are analog communication systems and digital communication systems. For an analog signal, the signal is varied continuously with respect to the information. In a digital signal, the information is encoded as a set of discrete values for example, a set of ones and zeros.
During the propagation and reception, the information contained in analog signals will inevitably be degraded by undesirable physical noise. The output of a transmitter is noise-free for all practical purposes. Commonly, the noise in a communication system can be expressed as adding or subtracting from the desirable signal in a completely random way.