ADDING EXTRA TELEPHONES

Evening Post, Volume CVII, Issue 61, 15 March 1924, Page 22

ADDING EXTRA TELEPHONES

■If more than one pair of 'phones is being used with a receiver, the operator either provides a special pair of terminals to connect each extra pair of wires, or falls back on the simple trick of tying the cord tips together with a bit of wire. There is a better way than either. Take a scrap of hard wood, ebonite brass—any old thing—and drill two holes in it big. enough to take the pin of the cord tip easily, and at" such a distance apart that when a tip is inserted into each hole the bodies of the tips jam together. Several seta can bo accommodated by means of extra pairs of fi? * • , c d«vice is' so inconspicuous that it does no harm to drill the holes in the panel close to the telephone terminals ; but it is as well to make an experiment with a piece of scrap to deteri?u? a j P r<>Per epa-cing of the holes. Ihis device will not work, unfortunately, when the 'phones are plugged into a jack, and the only thing to do, short of makmg a special plug that will accommodate the extra cord, is to provide terminals for extra telephones.' If this is wired so that the 'phones are in series, they must, of course, have a bridge when only one pair is in circuit. If the connections are parallel, this is not reijuired. The series connection of extra phones is usually best : it certainly is if there as any great difference between the ' resistances" of the telephone windings -A low ■resistance set connected in parallel with a.high resistance pair will take the lion's share of the current: