The front connector is plugged onto the module and covered by the front door. When replacing a module, only the front connector is disconnected, the time-intensive replacement of all wires is not necessary. In order to avoid errors when replacing modules, the front connector is coded mechanically when first plugged in. Then, it only fits in to the modules of the same type. This avoids, for example, an AC 230 V input signal accidentally being plugged into the DC 24 V module.

In addition, the connectors have a "pre-engagement position". This is where the connector is snapped onto the module before electrical contact is made. The connector clamps onto the module and can then easily be wired ("third hand"). After the wiring work, the connector is inserted further so that it makes contact.

The front connector contains:

• Contacts for the wiring connection.
• Strain relief for the wires.
• Reset key for resetting the front connector when replacing the module.
• Intake for coding element attachment. There are two coding elements on the modules with attachment. The attachments lock in when the front connector is connected for the first time.

The 40-pin front connector also comes with a locking screw for attaching and loosening the connector when replacing the module.

The front connectors are available for the following connection methods:

• Screw terminals
• Spring-loaded terminals