Sennheiser HD400 Instructions For Use Manual page 42

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HMEC 305-C NoiseGard™ headset
The HMEC 305-C differs from the HMEC 300 in the following features:
• No Mono/Stereo switch
• Connection of headphones and microphone via XLR-5 plug
HMEC 306 NoiseGard™ headset
The HMEC 306 differs from the HMEC 300 in the following features:
• Connection of headphones, microphone and NoiseGard™ electronics to the on-board
power supply system (12–35V DC) via 6-pin Redel plug
HMEC 322 NoiseGard™ headset
The HMEC 322 differs from the HMEC 300 in the following features:
• No Mono/Stereo switch
• Coiled cable
• Connection of headphones and microphone via U-174/U jack plug to a high impedance
interface in the helicopter