The I/O Terminal Units TU 715F (screw type terminal) and TU 716F (spring type terminal) are used as a socket for the I/O module, which exclusively incorporates inputs and outputs for 24V DC digital or analog signals.
The I/O modules (I/O expansion modules) are placed on the I/O Terminal Unit and locked into place using two mechanical locks. To loosen this connection a screwdriver should be inserted in the recess provided and the Terminal Units are carefully pulled away. All electrical connections are made through the Terminal Unit, which allows the removal and replacement of the I/O units without disturbing the wiring at the terminal unit.