Telegraph, Morse

A telegraph, characterized by the use of a relay, working a local circuit, which circuit contains a sounder, or recorder for giving dot and dash signals constituting the Morse alphabet. The signals are sent by a telegraph key, which when depre ed closes the circuit, and when released opens it. The two underlying conceptions of the Morse Telegraph system are the use of the dot and dash alphabet, and the use of the local circuit, which circuit includes a receiving instrument, and is worked by a relay, actuating a local battery. It would be difficult to indicate any invention in telegraphy which has had such far-reaching consequences as the one known as the Morse telegraph. In other places the principal apparatus of the system will be found described. The cut Fig. 318, repeated here gives the general disposition of a Morse system. (See Circuit, Local.) IMG:8956969607833025625_512F318.jpg: Fig. 318. DIAGRAM OF MORSE SYSTEM. 513   STANDARD ELECTRICAL DICTIONARY. The key by which the me ages are transmitted is shown in Fig. 319. M is a base plate of bra . A is a bra lever, mounted on an arbor G carried between adjustable set screws D. C is the anvil where contact is made by depre ing the key by the finger piece B of ebonite. E, Fl are adjusting screws for regulating the vertical play of the lever. H is the switch for opening or closing the circuit. It is opened for transmi ion, and closed for receiving. By screws, L L, with wing nuts, K K, the whole is screwed down to a table. IMG:8956969607833025625_513F319.jpg: Fig. 319. MORSE TELEGRAPH KEY. In the United States the simplest disposition of apparatus is generally used. The main line is kept on closed circuit. In it may be included a large number of relays at stations all along the line, each with its own local circuit. There may be fifty of such stations. Battery is generally placed at each end of the line. Very generally gravity batteries are used, although dynamos now tend to supplant them in important stations. As relays the ordinary relay is used. Its local circuit includes a sounder and local battery. The latter is very generally of the gravity type, but oxide of copper batteries (See Battery, Oxide of Copper) are now being introduced. At main or central offices, the terminals of the lines reach switch boards, where by spring-jacks and plugs, any desired circuits can be looped into the main circuit in series therewith. In European practise the main line is kept on open circuit. Polarized relays are used to work the local circuits. The currents for these have to be alternating in direction. When the line is not in use its ends are connected to earth at both ends, leaving the battery out of circuit. Each intermediate station has its own main, or line battery for use when it desires to send a me age. In the American system as first described, it will be seen that the main batteries are at most two in number. For the details of the different apparatus, the following definitions may be consulted: Embo er, Telegraphic--Recorder, Morse--Relay--Relay Connection--Sounder. 514   STANDARD ELECTRICAL DICTIONARY.