The left ear holds the battery and the cover easily slides down to get to the battery compartment, (Hint: the piece will look like PAC-MAN when you slide it off) what I discovered is that they say it can be powered for a 4.5v AC adapter but it does not have a built-in connection. So I wired one into mine and found that the power conversion is too great which leads to an over-amplification of sound thus a loud humming is broadcast with the audio feed. I will try a lower powered adapter (3v) and let you know.
Another nice feature is that you can tune in the FM frequency on older radios, because newer digital radios only let you go to 88.5 and above, and I believe this device broadcasts at 88.1 or 88.3!
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