Profibus connector switches

[rob63]

I was just wondering what is the purpose of the on/off switch on a Siemens profibus connector? As i understand it the end of line is always on but what is inside these switches and what is the purpose?

 

[boneless]

There is a termination resistor inside of the plug.

Reason why:
http://profibus.felser.ch/en/index.html?der_busabschluss_fuer_rs485.htm