Author Description

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 Excerpt:...covered by another sheet of paper upon which is laid the second sheet of foil. On top of this is laid the third sheet of paper and the whole is folded into a convenient bundle. The sheets of foil must be-well insulated from each other and the wires must project from the condenser. The ground connection is made by soldering a wire to a coldwater pipe. In the case of a portable set the ground may be made by driving a metal rod into the ground or sinking metal netting into a body of water. The telephone receivers cannot well be made and must therefore be bought. The type of 'phones used will therefore depend entirely on the builder's purse. The Sending Set The same aerial and ground are used for sending as were used for receiving, and for the experimenter, it will be far cheaper to buy a spark coil for his sending set than to attempt to make one. For a field set there will be very little need of a sending helix, as close tuning will be hardly possible; but for the stationary set this is very useful. The helix is made by building a drum with square heads fastened together by six or eight uprights, arranged on the circumference of a circle. On this then are wound ten or twelve turns of No. 10 or 12, brass or copper wire. Binding posts are fastened to the ends of the wire and variable contact made on the turns by means of metal spring clips. The spark gap is made of a hard-wood base with two uprights to which are fastened strips of brass. Under these strips are placed two pieces of battery zincs so as to make the gap between their ends variable. Binding posts are fastened to the strips for contact. The sending condenser is the same as the receiving in construction, but different in material. The dielectric is glass while the conducting surfaces are tin-foil, arra...