m-pod for Magstim EGI

What Is Optical Isolation?

A typical event marker is sent by changing the voltage on a wire from 0 to 5 volts. The signal wire and a ground wire connect sender and receiver directly:

Trouble arises when electrical “noise” is introduced, typically from nearby motors or fluorescent lighting. Optical isolation stops this noise in its tracks. It prevents electricity from flowing directly by illuminating an LED and placing a photosensor in front of it:

m-pod for Magstim EGI contains eight optical isolation chips, one for each line.

When to Use m-pod With StimTracker Instead

StimTracker offers more options than the combination of response pad + m-pod described above:

• Mark onset of auditory stimuli
• Use more than one light sensor
• Multiple outputs, e.g. one output to Net Amps and one to an eye tracker, guaranteeing that your data in Net Station and in the eye tracker are on the same timebase

Additionally, with the StimTracker Quad model, you can:

• Mark onset of a participant’s vocal response using a mic
• Accept direct TTL and switch inputs; this is handy for custom applications such as foot pedals or accepting input from other devices
• Have a direct TTL output connector, very useful when outputting to a recorder for which Cedrus does not have a ready-made m-pod model

Using m-pod with StimTracker is described on this page.