The MEG Sound and Intercom system
This is the sound delivery and intercom system in the MEG. It was designed and built by David Hayes.
The on/off buttons are on the back, and clearly indicated on the top of the case.
There's two clear control sections: three yellow knobs and two green ones.
The first three yellow controls are for setting the intercom part of the system. They control the volume of the MSR speaker, the desktop speaker and the MSR headphones, but only when using the intercom.
The second pair of green controls are for controlling the audio from and to the stimulus computer. The first one controls the recording volume of the MSR microphone and the second one sets the stimulus computer replay level. Replay is always through the headphones, although the sound can also be heard coming from the MSR loudspeaker.
These two sections are independent, so the green headphones volume control will not affect the volume of the intercom through the headphones!
All volumes are calibrated, and the default volume is with all controls in the 3 o'clock position, like in the picture. Please keep then in this position unless for a good reason, and always remember to put them back afterwards.
When recording subject voice responses, like in a naming task, the microphone volume needs to be set correctly to get a good quality recording. This is done with the first green control and can be checked with the volume indicator on the right side of the audio system's box (not on this photo).
Finally, the intercom has a microphone which has a switch for talking to the subject. The intercom is strictly one-way, so when you are talking you cannot hear the subject. The sound will always be replayed through both the MSR speaker as well as the MSR headphones. The switch should be pushed UP to talk, and will return to the middle position by itself, but if you push it DOWN it will stay that way. This could be very practical, as it allows you to talk to the subject with both hands free, but there's a risk of forgetting to put it back to the middle position! Please be careful. We do not want to be in a position where we cannot hear the subject, but they can hear all of our conversation!