Function symbols and their uses:
Shape like circles, squares, diamonds, hexagons, and lines used to represent the hardware and software instruments and functions as follows:
- Discrete Devices and Functions, represents discrete hardware instruments and functions that are implemented in non-microprocessor-based systems similar to single-case transmitters, controllers, indicators etc.
- Shared Devices and Functions, represents shared and distributed software analog instruments and functions that are implemented in microprocessor-based systems similar to distributed control or programmable logic control systems.
- Shared On–Off Devices and Functions, represents shared and distributed on–off software instruments and functions that are implemented in microprocessor-based control systems similar or equal to a distributed control or programmable logic control systems.
- Computer Devices and Functions, represents shared and distributed on–off software instruments and functions that are implemented in a computer-based control system
