Digital input/output modules connect the 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 modules offers the following advantages for users:

• Optimum adaptation:
  Using any desired arrangement of modules, the number of inputs/outputs can be matched to the task to be performed. Superfluous investments no longer exist.
• Flexible process connection:
  Digital actuators and sensors of various types are available for connecting the S7-400 to the process.