TTL signal to biopac

[JEC]

I am trying to get medialab to send signals to biopac in order to note physiological responses after the presentation of certain stimuli. I have been looking at previous posts but I'm afraid they are too advanced for me. Can anyone provide a simpler explanation of the parameters I need to create? Is it possible that the communication between the two computers might not take place because we are using a laptop to run biopac?
Any help would be greatly appreciated.

There have been some cases reported where a laptop's TTL output levels have been too low (3.3v) to work with external hardware. Most of the time, external hardware is expecting to see a 5.0v signal as a logic '1'.' Some laptops just don't send a strong enough signal to register.

One of our users did post a sample MediaLab experiment which successfully interfaces with an eye-tracking system:

http://www.empirisoft.com/support/showthread.php?t=152

Can you post a link to the Biopac system you're using?

Does anyone in your lab have access to an oscilloscope - or at the very least, a multimeter - that we could use for diagnosing the problem?
John