[NOTE: This text was originally drafted for Lightning Arresters (Registration Nos. 8459, 8460). These objects are no longer in the Collection. However, lightning arresters of similar type are incorporated in the Telegraph System Model (Registration No. ST 007076) and so this text has been linked to that object.]
8459 - 8460
Lightning Protection as used on Telegraph and Telephone Lines in Victoria
This instrument is made up in the form of two brass discs, 2-1/8 inches in diameter. The lower disc A is screwed to a stone base. A threaded brass rod, fixed centrally, rises from the base through a hole in A. A paper ring, resembling a wheel with 3 spokes, saturated with paraffin wax, is laid on A, and on this ring the other disc is laid, the rod passing through a central hole in B. The rod is insulated from A by an ebonite collar. B is pressed down on the paper ring by a threaded nut, so that a very small space - about 5/1000ths of an inch - is left between A and B. Three terminals are provided, the two outer being connected to A and the central one to B through the rod.
The Line wire is connected to A at one terminal and the ingoing wire to the office to the other A terminal. B is connected to earth by the central terminal. Atmospheric electricity affecting the line wire will jump from A to B and to earth in preference to passing through the instrument. Each line wire requires one guard. In Telephone Exchanges, where the number of wires is very large other forms are employed.