RS232-TTL Interface

The circuit matches the RS232 signal of a PLC to the TTL level of an Arduino.
By means of a pin header the Arduino is attached to the PCB.
Through the D-SUB connector a connection with the PLC is established. 
Further IO is provided by PCB terminals from WAGO:
X2: 5V
X3: Arduino D2
X4: GND

Furthermore, a potentiometer was installed to be able to apply a variable level to A0.

The MAX232 was used according to the typical application.