Wireless Telegraphy and Telephony Simply Explained / A Practical Treatise Embracing Complete and Detailed Explanations of the Theory and Practice of Modern Radio Apparatus and Its Present Day Applications, Together With a Chapter on the Possibilities of Its Future Development

by Alfred Powell Morgan

FIG. 118.—Breaking-in system.

There are two Codes in general use for wireless telegraph purposes, the Morse and Continental. It takes about five per cent. longer space of time to send a message in Continental than it does in Morse, but the former has the advantage of not containing any letters requiring proper spacing in order to be recognizable. American coastwise steamers use the Morse code; transatlantic ships use the Continental code.

One of the greatest disadvantages of most systems of wireless telegraphy lies in the fact that no arrangement is provided for simultaneously transmitting and receiving wireless signals. It is usually necessary for one operator listening to another to have to wait until the finish signal is given before he can reply or interrupt in case he cannot understand part of the message, because the receiving apparatus of the transmitting station is necessarily disconnected from the aerial and the ground during the period a message is being sent. If it were to be connected at this time the powerful currents of the transmitter would rush through the receiving apparatus into the ground without setting up any very powerful waves in the aerial and seriously injure the delicate receiving instruments.

The Breaking-in-System is a method of simultaneously transmitting and receiving wireless signals. This is accomplished by providing the transmitting key with a second set of contacts, so arranged that when the key is released between the dots and dashes of the code the aerial and ground are automatically connected to the receiving apparatus. When the key is pressed the receptor is automatically cut off. The advantages of such a system are more or less obvious. When interference or a misunderstanding occurs the fact can be immediately signaled to the sending operator, and the message commenced over again.

FIG. 119.—The receiving apparatus of the station at Nauen. The message is being printed on tape by a recording device.

CHAPTER VII. THE EAR. HOW WE HEAR. SOUND AND SOUND WAVES. THE VOCAL CHORDS. THE STRUCTURE OF SPEECH.

On either side of the head, lodged in a cavity which they do not completely fill, and situated in the midst of a dense and solid mass of bone, entering into the base of the skull and forming the temporal bone, are two membraneous bags called the membraneous labyrinth and the scala media of the cochlea. Each bag is filled with a liquid, and is also surrounded and supported by a fluid which fills the cavity in which they are lodged. Certain small, hard bodies, free to move around, lie in the fluid of the bag. The ends of the auditory nerve of hearing are distributed around the wall of the sac, so that they are subjected to the blows of the little particles of calcareous sand, or otoconia, as they are called, whenever the fluid in the bags is disturbed.

FIG. 120.—Diagram of the ear.