Activate a relay using laptop's parallel port

[hrgwea]

Hi, guys. I'm new here. Forgiveme if this is too newbie.

I have a relay that I want to switch on using one of the output pins on the parallel port.

This is what I've got:

The relay is powered by a 5V DC adapter and the transistor should act as a switch.
But i dont know where to connect the parallel port's ground pin.

If I just connect the 5V pin to the transistor's base (like the diagram shows), it doesn't work.

 

[Resqueline]

Ground to emitter/-5V. Add base resistor (value depends on port, transistor, & relay data).

 

[hrgwea]

It works. Thanks.