The SD-651 is designed to meet the performance criteria designated by UL. Its sensing chambers are sealed against back pressure air flow, dirt, and insects.
5-degree volume control levels, built-in 24V DC forced relay and selectable power (6W, 30W, 60W, 120W): these are only some of the best-in-class features of Honeywell’s volume controller range! Design
HN-A500I is a high efficient 500W Power/Booster amplifier provides audio signal amplification for public address and voice alarm system, It is reliable, efficient and light in weight.