8 in., Self-Amplified Clean Room Ceiling Speaker capable of reproducing voice paging in clean room environments and has a screwdriver adjustable volume control located on the 1 Watt amplifier circuit board. The speaker requires 24VDC, 50mA (1-power unit). Features: large rubber o-ring to seal the grille to the ceiling, rubber washers for all mounting hardware and a polycarbonate dust shield located between the speaker and the grille. – Self-Amplified. – Capable of Reproducing Voice Paging in Clean Room Environments. – Screwdriver Adjustable Volume Control. – 8″ Speaker.