Motorola PMMN4039 Guia Del Usuario página 5

DO NOT cover or block the rear opening at your RSM
back housing to prevent performance degradation. For
instance, wearing the RSM at chest or abdomen will
block the rear opening. When this happens, noise from
the environment will not reach the front and rear opening
of the RSM in an equal manner. As a result, the
performance of your RSM with this condition will be as
normal RSM without Noise Canceling function.
So, you are recommended to wear RSM at your
shoulder for optimum noise cancellation.
2) RSM can also be used for close talking (by hand-held 2
inches from your mouth). The noise canceling
performance by hand-held is almost comparable to the
performance of wearing the RSM at your shoulder.
The combination of radio, RSM and optional accessory
need to be worn properly, so that the RSM cord does not
cross over or touch either the radio antenna or optional
accessory.
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