. Western electrician . showthat the intervening period was suflliciently active and ex-acting to have had some influence in deciding .which wasthe fittest type of board for survival. That type was thecordboard, and it may be desirable now to trace briefly thedevelopment of the most generally used form of cordboardfor small exchanges. For this purpose it is necessary to call your attention toa patent specification which I think may be called a classicin this branch of invention. It is dated November 29,1S79, numbered 4,903, and granted to C. E. Scribner. Inthe universal jack-knife switch there
. Western electrician . showthat the intervening period was suflliciently active and ex-acting to have had some influence in deciding .which wasthe fittest type of board for survival. That type was thecordboard, and it may be desirable now to trace briefly thedevelopment of the most generally used form of cordboardfor small exchanges. For this purpose it is necessary to call your attention toa patent specification which I think may be called a classicin this branch of invention. It is dated November 29,1S79, numbered 4,903, and granted to C. E. Scribner. Inthe universal jack-knife switch there are the indicatorsand the individual connecting springs for the lines as in theBell board, but arranged in distinct groups, and there arethe horizontal connecting bars also. Although there arethese points of similarity, there are improvements overeach. In the Bell board the line comes to the indicatorfirst, then through the spring-jack to earth. Inserting aplug into the spring-jack cuts off the earth.^but the indicator. FIG. 5. THREE-PHASE WIRING AND LIGHTING FIXTURES IN CONCORD, N. H.—EXTERIOR WIRING FOR COURT-ROOM DOME. remains in circuit. Scribner cuts off both drop and earchin one. operation by the simple device of putting the dropon the earth side of the jack, so that both subscribers indica-tors are cut out of circuit instead of both remaining is another step forward. The horizontal connectingstrip is also improved by being turned round when connecting the two subscribers lines together, twocords were used, as in the Bell board, each cord having aplug at either end, and the calling subscribers linewas connected to the revolving bar by one cord, andthe same revolving bar connected to the called sub-scribers line by the other cord. But as both subscribersindicators were cut out, some provision must be madefor the reception of a disconnection signal. This switch-board brings us one more step forward in the inclusion ofsignaling apparatus in the connecti
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Keywords: ., bookcentury1800, bookdecade1880, bookidwesternelect, bookyear1887
