St. John, Thomas M. (Thomas Matthew), b. 1865 · New York, T. M. St. John · leaf 168
Fig. 253. 252, are largely used in all sorts of establishments, schools,etc., for ringing bells at certain stated periods. Thelower dial shown has many contadl-points that can beinserted to correspond to given times. As this revolves,the circuits are closed, one after the other, and it may beso set…
Electricity
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