 | Circuits, Formulas and Tables Electrical Engineering - Basic Vocational Knowledge |
 |  | 2. Bell Circuits |
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2.1. Direct-current Bell
Direct-current bell to be actuated from one place
Direct-current bell to be actuated from two places
Bell installation for reciprocal calls
Sell installation for reciprocal calls with key change-over switch
Bell installation for reciprocal calls with switch-on push-button, line-saving
Bell installation for reciprocal calls, line-saving
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