St. John, Thomas M. (Thomas Matthew), b. 1865 · New York, T. M. St. John · leaf 171
Fig. 259. etc., to indicate a certain room when a bell rings at the office. The bell indicates that some one has called, and the annunciator shows the location of the call bj displaying the number of the room Fig. 25S. or its location. Fig. 259 shows a small annunciator. They contain…
Electricity
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