Front connector Removable terminal block Terminal arm is not the same thing
The interface is generally fixed and connected to the adjacent module No, with Siemens S7300 for example
The terminal arm is the interface that is to be inserted behind the backplane bus.
The front connector is that we have to connect DI, DO, AI, AO those 20-pin plug, connected to the line after the insertion is to facilitate wiring and debugging designed to