Power Sources
Electric bells are typically designed to operate on low voltages of from 10 to 24 V AC or DC. Before widespread distribution of electric power, bells were necessarily powered by batteries, either wet-cell or dry-cell type. Bells used in early telephone systems derived current by a magneto generator cranked by the subscriber. In residential applications, a small bell-ringing transformer is usually used to power the doorbell circuit. So that bell circuits can be made with low-cost wiring methods, bell signal circuits are limited in voltage and power rating. Bells for industrial purposes may operate on other, higher, AC or DC voltages to match plant voltages or available standby battery systems.
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