Sennheiser SKM 1030 series Gebrauchsanleitung Seite 19

Muting the microphone
º
With switch you can mute the microphone of the hand-held transmitter without
switching off the transmitter itself. This avoids hissing noise in the receiver. The
" " and " " positions are clearly marked on the switch.
ON OFF
º
Switch can be locked in the ON position to avoid accidental switching (note the
position of the screw head):
ON OFF ON
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