DC Bells that vibrate emit a long, continuous ringing sound. As long as electricity is applied, the striker keeps banging the gong rapidly. The universal adaptaplate fits any single gang box, 3 1/4" (83mm), 3 1/2" (89mm), or 4" (102mm) octagon box, as well as any plaster cover with mounting holes spaced 2 3/4" (70mm) apart. It can also be mounted directly on a surface. 6 "additionally mount on 4" (102mm) square boxes 10" bells. When placed on a Cat. No. 449 weatherproof back box, the DC vibrating bell can be used in outdoor applications. Refer to Accessories. Timing, planning, and basic alarm applications are covered. DC bells that vibrate emit a long, continuous ringing sound. As long as electricity is applied, the striker will continue to rapidly strike the gong. The universal adaptaplate fits any single gang box, 3-1/4" (83mm), 3 1/2" (89mm), or 4" (102mm) octagon box, as well as any plaster cover with mounting holes spaced 2-3/4" (70mm) apart. It can also be mounted directly on a surface. Moreover, 6" and 10" bells install on 4" (102mm) square boxes. The DC vibrating bell can be mounted on the Cat. No. 449 waterproof back box for use in outdoor applications. The universal adaptaplate fits any single gang box, 3-1/4" (83mm), 3-1/2" (89mm), or 4" (102mm) octagon box, as well as any plaster cover with mounting holes spaced 2-3/4" (70mm) apart. It can also be mounted directly on a surface. Also mounting on 4" (102mm) square boxes are 6" and 10" bells. The DC vibrating bell can be mounted on the Cat. No. 449 waterproof back box for use in outdoor applications.