The ornamental design for an alarmhousing, as shown and described.
FIG. 1 is a perspective view of the alarm housing.
FIG. 2 is a front elevation view of thereof.
FIG. 3 is a first side elevation view thereof, the opposing side elevation view being a mirror image thereof.
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
In the drawings, the broken lines depict environmental subject matter only and form no part of the claimed design. The back view of the alarm housing illustrated in FIGS. 1-5 is hereby disclaimed and forms no part of the claimed design.