AUTOMATIC TRANSMISSION. 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 appa ratus is used which trebles, and in some eases quadruples the carrying capacity of a wire, se curing 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 operator strikes three punches, the central one producing a eentral hole, which is of no avail electrically, only car rying forward the paper ; the left-hand disk pro ducing two holes, directly opposite to each other, on the sides of this central row, and that on the right producing two holes, placed diagonally to each other. The passage of the electric current is regulated by the position of the outer holes; those opposite each other admit of a momentary passage of the current through the seeond por tion of the instrument, i.e., the 'transmitter,' which is used in sending the message, while the holes diagonally placed produce a lengthened mark corresponding to the dash. The following diagram represents the word 'and,' as shown on the punched slip: The way in which this is arranged will be seen from the illustrations. In the diagram 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 mak ing contacts on either side completes either of The third portion of this instrument is the 're ceiver,' in which the currents sent by the action of the punched slips in the transmitter are re produced in the dots and dashes of the Norse eode—the printing being, moreover, done with a mathematical accuracy which keying by hand cannot attain. The speed of transmission de pends on the length of the line and state of the atmosphere; but the movements of the eloek work, both of the transmitter and receiver, are capable of adjustment to any speed below 120 words per minute.
A system of multiplex telegraphy invented by Delany and employed in Europe provides for the simultaneous transmission of a number of mes sages either in the same direction or part in one direction and the remainder in the opposite di rection. The apparatus consists of a number of
contact pieces arranged on a circular disk or table, some of which are connected with the separate sending or transmitting instruments, while others are connected with local relays and batteries and the ground. 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 in struments 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 in genious synchronizing device keeps them always in unison. In this way it is possible to operate twelve different sets of Morse transmissions over one wire, and it is accomplished in the following manner. The first operator closes his key, and as the trailer passes around, it will make con tact with the line wire and his instrument will be connected about 36 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 correspond ing instrument at the other station, which is only in a position to receive the signals from the one transmitter. The same is true for the other operators and their instruments, each one employ ing the wire for a certain fraction of the time. Numerous other systems have been devised, im portant among which is the multiplex printing telegraph of Rowland, which has been successful ly used in Europe. 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.