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Design & Technology

Design activities

Systems diagrams

A system is a collection of parts that performs a function. A systems diagram is a representation of how a system will work. These are often used during the design process to generate ideas for electronic systems.

A simple systems diagram contains three boxes:

  • Input: the input starts the system, such as a switch or sensor.
  • Process: the mind of the system, which considers the inputs and decides what to do. Common process blocks include comparators, latches, logic gates, counters, timers and pulse generators.
  • Output: the system's response to being activated - eg a flashing light or a buzzer.

Each box in the system diagram has a specific function, and they are joined by a signal. Each box is normally a physical item: this could be a single component or a collection of components.

Systems diagram

Systems diagram

Systems diagram of a vending machine

Vending machine systems diagram


A complex system contains many inputs, processes and outputs. Some of these might form smaller systems - called 'sub-systems' - that work within the system. For example, the systems diagram for a car can have over 400 boxes and more than 10 sub-systems (including steering, braking, lighting etc).

Systems diagrams can be used to show how these different sub-systems relate to each other.

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