User Guide

5
The HMEC 250 headset
The HMEC 250 headset with NoiseGard 2.0 active noise
compensation features closed, dynamic, circumaural stereo
headphones. The HMEC 250 is a headset for general aviation
use.
NoiseGard 2.0
TM
The NoiseGard 2.0 active noise compensation system is
based on the principle of cancelling out sound using “anti-
sound” (phase-inverted sound). Tiny microphones pick up
low-frequency ambient noise (up to 1 kHz) near the ear. The
NoiseGard 2.0 electronics use this noise to generate a sound
wave which is the exact opposite (i.e.: at the same level but
polarity reversed – 180° out-of-phase), the result is that the
polarity reversed signal cancels most of the outside noise.
Fail safe operation
When the batteries are completely discharged, NoiseGard
automatically switches off. RT traffic (e.g. ATC) and
intercom will still be heard through the headphones.
Peak level protection
The peak level protection safeguards your ears from volume
peaks above 110 dB.
TalkThrough function (TT)
The TalkThrough function allows you to communicate with
the people around you while wearing the headset. The
NoiseGard active noise compensation and the peak level
protection remain unaffected by the TalkThrough function
and help to protect your hearing.