Herbert Treadwell Wade

“ For the generation of power in the electric telegraph, the gravity batteries (see Voltaic Cell or Battery) are chiefly employed in the United States. Various forms of the Daniell battery are also used, especially in Europe. The number of cells employed varies with the length of the line, the conditions of the wire as regards insulation, and the nature of the instruments used. It is quite common in the United States, especially in cities where many lines centre, to employ dynamos driven by steam engines for generating the current in place of batteries, or to make use of storage batteries. ”

“ A trailer or rapidly revolving arm connected with the line wire passes over these contact points so that the circuit is successively completed through the different instruments at one station, while a similar device at the other station, revolving synchronously with the first, makes connections with an equal number of instruments. The speed of revolution of the trailers is regulated by two tuning forks or vibrating reeds of the same pitch, and an ingenious synchronizing device keeps them always in unison. ”

“ In the previous description of the Morse system, we have assumed the instrument to be worked directly by the current sent along the line. On long circuits, however, direct working could only be accomplished by great battery power, owing to inevitable loss by leakage, experienced by a current before it reaches its destination. Consequently what is known as a relay is used and the sounder or recording instrument is worked by a ‘local current’ derived from a local battery at the receiving station. ”

“ The first operator closes his key, and as the trailer passes around, it will make contact with the line wire and his instrument will be connected about 30 times in one second, thus transmitting that number of impulses. Now, if he desires to send a signal corresponding to a dot, he would close his key for a brief interval, which may be one-twelfth of a second, thus allowing three impulses of current to be transmitted over the line wire to the corresponding instrument at the other station, which is only in a position to receive the signals from the one transmitter. ”

“ In pole and over-house lines, the wires are kept from each other and the current from escaping to the earth by insulators of glass. In Europe white porcelain and brown stoneware insulators are used, and the former substance, when of good quality, well glazed and well burned, is perhaps the most perfect of all insulating materials, and does not deteriorate with age. The fewer the poles on which the wires are suspended, the better is the insulation and the less the cost, but the liability to accident is greater. ”

“ POLARIZED RELAY.
The way in which this is arranged will be seen from the illustrations. In the diagram n s is a hard steel permanent magnet, whose south end, s, has a slit in which the soft iron armature a is pivoted. To this armature a thin aluminum tongue, b, is attached, which by making contacts on either side completes either of two local circuits, and operates either of two sounders, according to which side the tongue is attracted. The coils on the magnet are so connected that a positive current attracts the tongue to one side, while a negative current attracts it to the other. ”

“ The key and battery are common to both circuits, the points of divergence being at the relay and at the ground. If the key at one station is depressed the current will flow through both sets of coils of the relay at this station without producing any magnetizing effect, but at the distant station it will traverse but one set of coils and will accordingly cause the relay to operate the local sounder. ”

“ The coils are wound with insulated wire and are inclosed in cylinders of hard rubber or vulcanite. Supported by an upright casting of brass is a lever balanced on the points of two screws, which carries transversely to its length an armature of soft iron. This piece of iron is directly above the poles of the electro-magnet, so that when the current passes through the coils it is attracted with sufficient force to produce a sharp click when a screw at its end strikes the surface of the metal. ”

“ In sending a message the switch is first opened and then the key is depressed. A current of electricity will pass from the battery along the line wire, around the magnets, drawing down the armature and making a click; thence down to the earth plates and through the earth back to the battery.
The operator at the sending station in transmitting a message opens his switch and depresses his key, so as to send a series of dots and dashes corresponding to the letters to be sent to the distant station. ”

“ The speed of the ordinary Morse instrument is limited to the rapidity with which the hand of the operator can move the key, and averages about 25 to 40 words a minute. To increase speed automatic apparatus is used which trebles, and in some cases quadruples the carrying capacity of a wire, securing at the same time mechanical accuracy in the relative size of the dots, dashes, spaces, etc. To effect this, three different instruments are required: First, there is a perforator, by which holes are punched in a paper slip to correspond with the signals required. ”

“ The receiving instrument connected to the line instead of being made heavy enough to give an audible sound by which the signal may be understood, is made extremely light and delicate so that it can be operated by a weak current. ”

“ In its simplest form the Morse telegraph includes a battery or other source of current, a key to break the circuit, and a line wire connecting with a sounder or recording apparatus at the distant station, the return circuit to the battery being formed either by another wire or by the ground. To send signals in either direction a sounder and key must be provided at each station. ”

“ It employs an alternating current and four transmitters and receivers can be used in connection with one wire. There is a mechanical keyboard somewhat similar to that of a typewriter, while the signals are received and printed on a tape or upon ordinary letter pages in ‘typewriting’ characters.
In the United States the telegraph is entirely in the hands of private companies. The first company was organized in 1845 under the name of the Magnetic Telegraph Company by Morse's supporters and associates. ”

“ The difficulty of using frictional machines, the only method for producing electricity then known, however, prevented the attainment of any practical results in this direction before the discovery of the voltaic cell. ”

“ The telegraph business of the United States is at present controlled by the Western Union and Postal Telegraph-Cable companies. The former in 1901 had 193,589 miles of poles and cable, 972,766 miles of wire, 23,238 offices, transmitted 65,657,049 messages, had receipts aggregating $26,354,151, expenses amounting to $19,668,903, and profits of $6,685,248. The average toll per message in 1870 was 75.5 cents, while the cost of transmission was 51.2 cents. ”