Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879 edition. Excerpt: ... be very rigid, otherwise the plate will be kept Ohm, the unit of resistance. tight to the magnets all the time; and one of the conditions of success in working is, that this plate shall be as close as possible to the magnet-ends, but not to touch; therefore fix the board tight, and adjust the magnets by means of the button shown on the top of them in the perspective figure. "The sounds to be transmitted, of whatever sort they may be, are to be made on the side p (Fig. 24); and likewise, when the instrument is used as a receiver, the ear is to be applied at the same place. A tube about two inches in diameter may be made fast to the front of the board, in a line with the centre of the plate; this will aid somewhat in hear ing. When two or three persons are to sing, it will be best to have each one supplied with a tube to sing through; one end of the tube to be placed close to the front of the plate. The sound of musical instruments, such as the flute and the cornet, will be reproduced much louder, if the front of such instrument be allowed to rest upon the rim of the hole in the board, just in front of the plate." It is specially noticeable that low talking can be heard more distinctly than when a great effort is made; but the sounds, though distinct, are not strong at any time, and other sounds seriously interfere with hearing. It is probable that some way will hereafter be devised for increasing the usefulness of the invention by increasing the volume of sound. On account of the weakness of the sound, it becomes necessary to provide a call to attract the attention of one in the room. This may be accomplished by having a small electric-bell worked by a one-or two-cell battery. Another way, quite as eff1cient, is to have a rod of...
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