. American telephone practice . utter and thus hold it in its raised position. Ascrew, /, passing through the front plate, /\ serves not only to hold 188 AMERICAN TELEPHONE PRACTICE. the magnet in place, but to hold the core in its place within the terminals of the coil are led out through two small holes in thearmature, and are connected with the terminals, h i, mounted on aninsulating strip, carried on the bracket, f. These drops should be so nicely made that the armature, d, willfit closely against the end of the tube, c, in such manner as to almostcompletely close the magnetic ci
. American telephone practice . utter and thus hold it in its raised position. Ascrew, /, passing through the front plate, /\ serves not only to hold 188 AMERICAN TELEPHONE PRACTICE. the magnet in place, but to hold the core in its place within the terminals of the coil are led out through two small holes in thearmature, and are connected with the terminals, h i, mounted on aninsulating strip, carried on the bracket, f. These drops should be so nicely made that the armature, d, willfit closely against the end of the tube, c, in such manner as to almostcompletely close the magnetic circuit in which the coil is placed. Thelines of force generated by the passage of a current through thecoil follow almost entirely the path provided for them by the shelland the core of the magnet, thus not only producing a very efficientelectromagnet, but also preventing any of the lines of force fromextending beyond the limits of the shell. These drops are usuallywound to a resistance of 500 ohms, and may be mounted as closely. FIG. OF TEN DROPS. together as desired without producing perceptible cross-talk. Theimpedance due to the great number of turns in the coil, and to theperfect magnetic circuit surrounding the same, is so great that prac-tically no diminution in the strength of speech transmission is feltdue to its being bridged across the line. In the modern construction of the Warner Drop, instead of therearwardly extending bracket being provided for carrying the ter-minals of the coil, these terminals are made in the shape of heavypins of brass, firmly screwed into the rear head of the coil, and tothese pins the terminals of the coil winding are soldered. Thesepins project through the armature of the coil in substantially thesame manner as in the original Warner Drop, and form terminals ofsufficient strength to need no outer support. MAGNETO SWITCH-BOARD FOR SMALL EXCHANGES. 189 The Warner type of drop has proved so satisfactory and is of suchcompact constru
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