Version DSL

I am new to Version DSL and have two questions.  I have a WESTELL 6100 modem. 

Is there any way to shut off the DSL connection (to install things in an off-line mode) other than switching the power switch on the modem off?  Can I do this with a software setting?

What is happening when I can't browse and get the message "network cable is unplugged" and then a few seconds later everything is ok?

 

Thanks,

Mike