How to find if the input module is sinking or sourcing?

Hi guys,

How to find out if the input module I am going to use is sinking or sourcing? It's important to know so that I can decide which type of sensors I'm going to use PNP or NPN. Is this information written in the manual or just the wiring diagram gives the clue? I don't seem to figure it out. The PLC is S7-300 but I'm asking this question not only for S7-300s but generally because I have to deal with almost all types of Siemens PLCs therefore I should know how to find this information for any type. Please be a little descriptive with your answer so that I can understand properly.

Thanks!

The specification for the module will detail the type of input. For instance, for the ET-200MP DI 16x24VDC BA (6ES7 521-1BH10-0AA0): 6ES7521-1BH10-0AA0 technical data shows. 

The FAQ What is the meaning of the terms "sinking" (German: "P-lesend") and "sourcing" (German: "M-lesend") in digital modules of SIMATIC?  helps you interpret what the module specs are telling you (and has a list of many of the modules with their sourcing/sinking type).