The Chicago loudspeaker and the junction box used to house the hub were designed to meet Chicago’s stringent requirements .The enclosure and junction box are made of steel. The cabling is contained within flexible metal tubing (FMT) listed for use in plenums and other air handling spaces. Where it enters the enclosure, this specialized conduit terminates in one-piece zinc connector fitted with rubberized polymer gasket forming the smoke-tight seal required by the NEC. The junction box is also sealed. A flame retardant fabric located below the speaker grille prevents the accumulation of dust.