Digital input/output modules are used to interface binary process signals to the S7-400. Digital sensors and actuators can be connected to the SIMATIC S7-400 via these modules.

Use of the digital input/output modules offers users the following advantages:

• Optimal adaptation:
  The number of inputs/outputs can be adapted to the corresponding task with the help of modules which can be combined as required. Superfluous investments are avoided.
• Flexible process connection:
  The S7-400 can be connected to the process via many different digital actuators and sensors.