The F-4436 and F-4431 Series Bells provide an easy low cost solution for all bell ringing applications. They are available in both 24 VAC and 120 VAC 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 24 VAC bells a bell transformer will be required. The transformer size is determined by the number of bells on the system. ATS provides optional, 2 amp and 4 amp built-in, bell transformers for some of the MC Series Master clocks. External mounted transformer assemblies such as the 8901-1821 and the 8901-1411 can be used for larger systems. For Plug-n-Play Bell systems see the AP21-BP1 and the MC41-BP1 brochures.