ART Pro Audio SLA4 - 4x140W Power Amplifier - Manual (Page 7)

SECURITY COVER
For commercial installations it may be desirable to set the gain controls
on the power amp, and then make them inaccessible to non-qualified
operators. This can be accomplished by using the Security Cover Plate
that is included with the SLA-4.
Simply set the channel level controls to the desired gain settings and
press the knobs into the chassis until they lock into their recessed
position. Then remove the two small phillips head screws, one on each
side of the four channel level controls. Use these same screws to
attach the security cover plate to the front panel, thereby covering the
four channel level controls, making them tamperproof.
See diagram below
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