A transmitter (information source) that takes information and converts it to a signal for transmission - A transmission medium over which the signal is transmitted - A receiver (information sink) that receives and converts the signal back into required informationFor example, consider a radio broadcast. In this case the broadcast tower is the transmitter, the radio is the receiver and the transmission medium is free space. Often telecommunication systems are two-way and devices act as both a transmitter and receiver or transceiver. For example, a mobile phone is a transceiver. Telecommunication over a phone line 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 receivers. Marconi’s means of communications over his wireless telegraph system was by Morse code, a series of dots and dashes created by American Samuel Morse. There were two variants, a dot or a dash and digital television is based on the same principle 1’s and 0’s as in the binary code. Television signals can either be analogue or digital. In an analogue 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, the binary code.