Page:Popular Science Monthly Volume 92.djvu/969

 Popular Science Monthly

��953

��were it not for the difficulty of learning the code sufficiently to understand what comes over the wire. And it is to make possible a line which sends automatically and automatically translates its signals that the device illustrated herewith was developed.

The principle made use of involves the so-called "step by step" method of pro- ducing synchronous motions at separated points and makes use of the ordinary tele- graph sounders and keys and the ordinary battery.

Reference to the drawings will show that there is provided a flat wooden wheel having around its periphery forty di- visions to correspond to the forty neces- sary characters of the alphabet including the numerals and the necessary punctua- tion marks. To the shaft of this wheel is rigidly attached a thin metal rachet wheel,

���The wood wheel with a thin ratchet wheel attached to turn it as the sounder works

such as can be purchased at the store of any gear supply dealer, having forty teeth. This shaft is mounted to rotate rather stiffly between bearings formed by screws having holes drilled in the tips, the shaft being pointed at either end to bear in the holes. The bearing screws are mounted in wood pedestals, as suggested by the drawings, and the whole mounted on a suitable base. A telegraph sounder, or any similar arrangement of magnets and lever, is arranged under the wheel and has mounted at the end of the lever a thin piece of spring metal which is bent so as to form a hook to engage with the ratchet. As will readily be seen this arrangement causes the letter wheel to revolve through the space occupied by one letter every

��time the sounder arm is drawn down. There is also another piece of flat spring metal to prevent the wheel going back- wards and also to press on the ratchet continuously so as to prevent it turning too freely and thus getting out of time.

From the above description, the use of the apparatus will be plain. There is provided at each end of the line one of the letter wheel machines, a telegraph key and a battery, all connected in series as in an ordinary telegraph line. When one wishes to transmit he opens his key lever and makes "dots" until the letter he wishes comes to the opening in the shield over the type wheel, then he pauses long enough to let the receiver know that that letter is to be copied, then proceeds to the next letter and so on. The end of a word is signified by a space, and the end of a sentence by a period or question mark. The method is, by its very nature, slow, but is quite accurate, which is more than can be said of the ordinary amateur Morse line. After some practice, fair speed can be obtained though.

Certain refinements naturally suggest themselves to the amateur — such, for instance, as having an extra wire or a duplex circuit to force a strip of paper up against the wheel, which would have rubber type set on it, thus producing a printing telegraph. It is also evident that the line described is a closed circuit line and consequently gravity batteries should be used as the current flows all the time when no message is being sent. This is, of course, the most reliable type of line, but there arc many well-known ways of producing an open circuit line on which ordinary dry batteries may be used.

Another method requiring a fair amount of interesting developing work is to use low frequency alternating current produced by a magneto generator to operate the apparatus. Thus, when it is desired to send a letter, the key is simply held down till the natural pulsation of the current has brought round the proper letter, when it is released for a moment. This method is entirely practical and well worth the trouble of constructing it. On lines running more than 100 ft. it is very desirable to use relays, as the current re- quired to operate the letter wheels is too much to transmit any distance without serious loss in the line.— Chas. Horton.

�� �