F-4436 and F-4431 series bells provide an easy low cost solution for all bell ringing applications. They are available in both 24/120VAC versions. They are easily controlled using any of the MC series master clocks, or for smaller schools or factories the AP21LV time switch can be used. For 24VAC bells, a bell transformer will be required. The transformer size is determined by the number of bells on the system. ATS provides optional, 2A and 4A built-in, bell transformers for some of the MC series master clocks. External mounted transformer assemblies such as the 8901-1821 can be used for larger systems.