Edward 340 Series are vibrating bells that produce a long, continuous ringing sound. The striker continues to strike the gong in rapid-fire as long as current is applied. Specified for timing, scheduling, paging and general alarm applications. Can be used in outdoor applications with the addition of an approved box. Full cast grids available for 4" bells. Universal Adaptaplate mounts directly on surface or fits any single-gang box, 3 1/4 inch (83 mm), 3 1/2 inch (89 mm), or any plaster cover with mounting holes on 2 3/4 inch (70 mm) centers. 6 inch and 10 inch bells also mount on 4 inch(102 mm) square boxes