The communication modules have the following mechanical features:

• Rugged plastic enclosure
• LEDs:
  for displaying "Send", "Receive" and "Error".
• 1 (CP 441-1) or 2 (CP 441-2) slots for plug-in interface modules. Interface modules for the physical transmission media RS 232C (V.24), RS 422/485 or 20 mA (TTY) can be plugged into the slots

The CP 441-2 and CP 441-2 can also be operated in expansion racks. However, transmission of the K bus signals must be guaranteed here.

Drivers

Different loadable drivers are available for the CP 441-2:

• Modbus:
  For communication according to the Modbus protocol with RTU format:
  • Modbus master; master-slave interfacing with SIMATIC S7 as master.
  • Modbus slave; master-slave interfacing with SIMATIC S7 as slave, message frame traffic from slave to slave not possible.

The two serial interfaces of the CP 441-2 can be operated independently of each other with different standard protocols or loadable drivers together with the V.24/TTY/X.27 interface modules.