Babcock SV BSVEA48X96D2N165R LPCW ShpDr11 thermal release mechanism vent covers open thermally by heat at fusible link temperature 360ff 12 manual operation vent covers open with internal and external manual pull handles 1/16 dia sst cable close vent at rooftop 13 electrical release/control none 14 burglar bars n/a smoke vent size 48 width x 96 length patent pending bsvea48x96d1n165r lpcw dwg no alum mill sngll