Laird & Lee's Vest-Pocket Practical Compend of Electricity; Thorough Instruction in Theory and Application

Laird & Lee's Vest-Pocket Practical Compend of Electricity; Thorough Instruction in Theory and Application

By (author) 

List price: US$15.84

Currently unavailable

Add to wishlist

AbeBooks may have this title (opens in new window).

Try AbeBooks


This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 edition. Excerpt: ... station. When number I, for example, wishes to talk with number 3, he moves the lever of his switch to the point marked 3, and after "ringing up," can carry on a conversation. In this system, the switch lever must always be moved back to a particular contact point when conversation is finished--that is, each telephone must remain con Fig. 77. nected to a particular one of the wires, so that other telephones may always be placed in communication with it by connecting to that particular wire. A Telephone Exchange System consists of a number of lines extending from substations to a central office switchboard, with means, at the switchboard, for uniting any two of the lines for conversation. In such a system, in order to be placed in communication with another subscriber, it is necessary to signal the central office and give an order to the operator, who will then make the connection desired. Switchboards are of many kinds, ranging from the multiple switch-boards used in large cities, in which as many as ten thousand lines are centered, to the simple affairs accomodating only a few lines. Each line entering the switch-board is provided with a terminal socket called a spring-jack, adapted to receive one of a pair of switchplugs forming the terminals of a flexible conducting cord. Two lines are united by inserting one of the pair of plugs into the springjack of one lins, and the other plug of the pa: r into the springjack of the other line, the lines being thus linked together by the cord circuit which unites the plugs. Each line entering the switchboard is also connected to a signal-receiving instrument in the board peculiar to that line. In small boards these line signals are usually annunciators, or "drops" as they more

Product details

  • Paperback | 48 pages
  • 189 x 246 x 3mm | 104g
  • United States
  • English
  • black & white illustrations
  • 1236986636
  • 9781236986634