Digital input/output (DIO)

A digital signal is a signal that exists in one of two states: high or low, open or closed, on or off. A digital input/output (DIO) device is hardware that sends or receives these digital signals. DIO devices are usually built around simple relays such as reed relays. These relays are normally open but close when power is sent to them. When the relay closes, it sends a signal that communicates a message or triggers another device.

DIO devices can be either input only, providing input from sensors; output only, sending signals to activate a device; or bidirectional, providing both input and output signals.

• Alarm
  • Digital input sensors can be used to detect an abnormal condition such as heat or water and trigger a relay causing an alarm to sound.
  
  
• Industrial controls
  • Programmable Logic Controllers (PLCs), commonly used in manufacturing, are industrial devices that provide a hardware interface for DIO signals.
  
  
• Hobbyists
  • Because DIO devices are extremely versatile and can often be controlled from home computers, they find many uses in hobbies such as model railroading and robotics.