The receiver illustrated herewith is to be used in connection with the transmitter described elsewhere in this volume. The body of the receiver, A, is made of a large wooden ribbon spool. One end is removed entirely, the other sawed in two on the line C and a flange, F, is cut on the wood, 1/8 in. wide and 1/16 in. deep. A flange the same size is made on the end D that was sawed off, and the outside part tapered toward the hole as shown. The magnet is made of a 30-penny nail, B, cut to the length of the spool, and a coil of wire, E, wound on the head end. The coil is 1 in. long, made up of four layers of No. 22 gauge copper magnet wire, allowing the ends to extend out about 6 in. The nail with the coil is then put into the hole of the spool as shown. The diaphragm C, which is the essential part of the instrument, should be made as carefully as possible from ferrotype tin, commonly called tintype tin. The diaphragm is placed between the flanges on the spool and the end D that was sawed off. The end piece and diaphragm are both fastened to the spool with two or three slender wood screws, as shown.
A small wooden or fiber end, G, is fitted with two binding posts which are connected to the ends of the wire left projecting from the magnet winding. The binding posts are attached to the line and a trial given. The proper distance must be found between the diaphragm and the head of the nail. This can be accomplished by moving the nail and magnet in the hole of the spool. When the distance to produce the right sound is found, the nail and magnet can be made fast by filling the open space with melted sealing wax. The end G is now fastened to the end of the spool, and the receiver is ready for use.