File:The practical telephone handbook and guide to the telephonic exchange (1906) (14756182645).jpg

Identifier: practicaltelepho00pool (find matches)
Title: The practical telephone handbook and guide to the telephonic exchange
Year: 1906 (1900s)
Authors: Poole, Joseph
Subjects: Telephone
Publisher: New York, Macmillan Co.
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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and next to the I.D.F. When a heat coil fuses, the corresponding line inside isearthed, and its lamp is lit on the switch-board ; but as nocommunication can be obtained, the operator reports the lineto the fault clerk. For convenience of connecting the twin jumper wires, theclamping screw a is connected to one of the inner-line springs,but is otherwise insulated, and is furnished with a soldering tabon the opposite side of the frame plate, so that both jumperwires can be connected on one side. Resetting Heat Coils.—In some recent forms of protector usedin America the heat coils are so constructed that they can beused over and over again without repairs. In the Kaisling protector this is accomplished by making the heat coilsymmetrical, so as to be reversible. When the coil has operated,and the pin has been pressed inward, all that is needed to resetis to reverse the coil, the pin having again become fixed, withits end projecting through the other end of the coil. APPARATUS-ROOM 286a
Text Appearing After Image:
Fig. 291a Side Elevation Plan Main Frame. Combination Protector and Fuse Strips APPARATUS-ROOM 367 In the Cook form the coil is pivoted, and is furnishedwith ratchet teeth. A spring is held outwards by one olthese teeth, but when the solder melts the coil moves round,and the spring is released. The solder hardens, and all thatis required to reset is to pull out the alarm spring until it iscaught by another tooth of the ratchet. Jumper Wires.—The jumper wires used on the mainframe are twin No. 22 B.W.G., each wire being tinned andcovered with rubber and cotton, the two wires having dis-tinguishing colours. The outer covering is braided cotton,painted with asbestos paint to render it flame-proof. Thewires used for ordinary subscribers lines are covered white,those for junction lines red, and those for private lines black. Cross-Connecting.—In connecting up, the jumper wires aresoldered to the two inner spring tabs of the arresters; theypass through holes in the wooden channel strips

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