Lessons in elementary physics / by Balfour Stewart.

  • Balfour Stewart
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Lessons in elementary physics / by Balfour Stewart. Source: Wellcome Collection.

    467/502 page 447
    not be supposed that the current actually traverses the earth. The action of the earth is to keep the points connected with the earth at one potential, and when this is the case the current Line Fig. 141. will have the same strength as if these points were in actual contact. Using single-stroke bells it is easy to arrange a simple code of signals depending on the number of strokes on the bell. When signals have to be sent from and received at two stations, a special form of key, called the Morse Key, is used at each station. Fig. 142 shows such a key ; it consists of a brass lever pivoted at /, which, when not in use, is held down by means of a spring j, so that the contact at b is closed, but on pressing the handle H, this contact is broken and that at a is made. The electrical connections, between the two stations are seen H in Fig. 143. When the station I is signalling to station II the circuit is complete through the contacts at a at I and h' at II. But-ifTI signals to 1 the'circuit is complete through the con- tactS (j'‘and h. The vibrating or trembling bell is ordinarily used as a call
    No text description is available for this image
    No text description is available for this image
    No text description is available for this image