The function of the electronic parts in these systems is to receive input information, to process this information and then to produce an output. For example, in a computer, the input information is provided by pressing the buttons on a keyboard, the processing may involve arithmetic or comparison with previous information in a memory and the output will be a print out or a display on a video display unit. In another example, both input and output of a communications system may be sound such as words or music.
In other areas such as instrumentation and control, these are many non-electronic systems widely used. Both power steering and servo assisted brakes in automobiles are usually non-electronic and mechanical clocks and watches still have a share of the market.
Electronic systems are required to process or react to information. The information may have many forms, including physical quantities such as temperatures, velocity or mass, simple on/off information resulting from a switch being operated, or the highly concentrated and detailed information in speech, music and pictures. All these different forms of information have one common factor i.e. both amplitude and frequency may vary with time. This means that they can be illustrated by means of graphs and in many cases they can be defined as functions of time with mathematical expressions. Electronic circuit's can only react to information in the form of time-varying voltages and currents.
We can conveniently refer to these forms of information as signals. There must therefore be some form of interface or converter between the real world and the electronic world. The interface may simply be a transducer for example; a microphone converts sound energy containing information into electrical energy in the form of a signal which contains the same information.
An electronic system will have input signals from transducers and output signals which are reconverted by other transducers to produce energy in various required forms. Between these two processes, within the system there will be other signal forms. Lets quickly look at the function of electronic circuit any systems. And the function is to process signal, many different processes are possible and useful but, before considering a wide range of processes, it will be helpful to examine some simple system and to consider what type of processes may be required.
A radio communication system: requires transmitting speech and music from a concert Hall to a place 100 miles away while other similar transmission is occurring in the same area.
While the problems are: Alternating signals (A.C.) can result in radiated electromagnetic waves (radio signals) but signals at audio frequencies do not radiate efficiently. Also, as there would be similar transmissions in the same area, there would be interference as all the radiated signals would be received more or less equality.
The solution use higher frequencies which can be radiated readily, in order to carry the signal information on these higher frequencies, use different high frequency carriers for each separate transmission to avoid interferences.
The process required is: The minimum needed for a simple radio communication system can be represented in the block system. Let's look at am automatic washing machine. The