St. John, Thomas M. (Thomas Matthew), b. 1865 · New York, T. M. St. John · leaf 48
Fig. 53- Fig- 54- niture. Fig. 54 shows a combination of push-button,speaking-tube, and letter-box used in citj apartmenthouses. Fig. 55 shows an Indicating Push. The buzzerindicates, by the sound, whether the call has been heard;that is, the person called answers back. Modijicaiions of ordinary-… … Fig. 55. Apparatus Book, Cliapter III., for home-made push-buttons.)62. Switches have a movable bar or plug of metal, moving on a pivot, to make or break a circuit, or transfer a current from one conduiftor to another.Fig. 56 shows a single point switch. The cur-rent entering the pivoted arm can go…
Electricity
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