Systems

A system is a set of components arranged to carry out a particular function. Systems may include mechanical, electrical or electronic components. The block diagram below represents a system for producing a batch of leaflets.

• Input is what goes into the system - the raw materials. In a music system the input usually comes from a CD player or radio tuner.
• Process is the shaping and forming of the materials, or the exchange of information needed to effect the output. In a music system it is the amplifier that does the processing.
• Output is what comes out of the system - the finished product. In a music system, the speakers take care of the output.

System feedback

Most systems have a fourth element - feedback - which is simply a way of changing the input or process as a result of what happens at the output. In a music system, feedback is a human response to the output from the speakers: if the music is too loud, or the radio tuned to the wrong station, the user will reduce the volume or retune the radio. In a system diagram feedback is shown like this:

An example of feedback in a production system is checking that the product meets the specification, and adjusting the process to make sure it does. Many systems have an automatic type of feedback, where feedback from one part of the system switches another part of the system on or off. This sort of system is called a closed system.