Sennheiser HMD120 Instructions For Use Manual page 7

HMD 120 headset
The HMD 120 differs from the HME 100 in the following features:
No Mono/Stereo switch
Coiled cable
M-87/AIC dynamic microphone and low impedance headphones
Connection of headphones and microphone via U-174/U jack plug to a low impedance interface
in the helicopter
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