The transmission of the six pulses of al ternating polarity for each letter of the Buck ingham alphabet operates a polarized relay in the main line at the receiving station, which relay by its armature controls two local cir cuits, in which are a governing relay, a unison magnet and an escapement magnet, the latter imparting, by means of an escapement, a step by-step motion to a *sunflower,* or distributor, of peculiar construction, to such purpose that, with the co-operation of the governing relay, and depending on the duration of the received pulses and the order of their arrival, one or more selecting relays are operated, and these, in turn, cause the operation of the type-moving levers which bring a desired letter on the type wheel to the printing position. Hence the Buckingham pnnter is a positive or 1step-by step* system in which an escape-wheel, and with it the sunflower, is caused by a cycle of six pulses of current, one or more of which are prolonged, to undergo a cycle of six steps for each letter or character selected and printed_ Consult author's (American Telegraphy and Encyclopedia of the Telegraph) for details of this system).
The Barclay Page Printer.— This system is a modification of the Buckingham page printer just briefly described. The operation of the Barclay printer up to the selecting re lays is virtually similar to that of the Buck ingham. At this point, in the Barclay arrange ment the selecting relays, instead of operating the type-wheel shaft, are caused to select a given one of 30 or 32 electromagnets, each of which controls or operates a certain type of a typewriter tvhich pnnts the letter; the message being printed by the typewriter in the ordinary way, by the aid of electrical devices. Messages may be transmitted by this system by means of a keyboard manipulated by an operator, or by means of perforated paper.
Murray Page Printer.—This printer is being used on the lines of the British Post office. The messages to be transmitted are prepared somewhat as in the case of the method utilized in the Wheatstone automatic system. The perforated paper sends certain combinations of electrical pulsations for any given letter over a main line and these pulsa tions in turn operate apparatus at the receiv ing station which perforates a paper strip in a manner corresponding to the letters trans mitted. This paper is then caused to pass before a set of metal strips which in their operation, and depending on the combination of perforations in the paper, select a certain letter of a typewriter, the message being thereby printed in page form. This system depends on synchronous movements of the transmitting and receiving apparatus, which is maintained by the action of the received pulsations upon apparatus in a local circuit at the receiving station. The speed of this system is about 103 words per minute. Consult Trans. Am. Inst. El. Ehgrs., 1901.
Baudot Multiple Printer.— This system is in successful operation on many of the tele !graph lines of the French government. For its multiplex feature it emp devices prac tically similar to those descirZed herein rela tive to Synchronous Multiplex Telegraphy. A keyboard is used, and letters are transmitted by depressing a given key which sends out the necessary combination of pulsations to repro duce a given letter at the receiving end, where by suitable selecting relays the given letter is selected and printed. The rate of signaling by this system is about 120 words per minute on one circuit. Consult Thomas' 'Traits de Telegraphique Electrique' ; also Electrical Re view, New York, 12 April 1899.
The Multiplex Printing Telegraph System.
In this country and in Great Britain a suc cessful printing telegraph system based largely on the Baudot and Murray systems has been recently developed and by means of which eight and 12 messages are sent on one wire simul taneously at a rate of 40 and 30 words respec tively, per minute.
A brief description of this system may be essayed here. In one respect it resembles the synchronous multiplex system previously de scribed herein.
Thus it employs a number of insulated seg ments arranged circularly at each end of the circuit and over which a revolving brush or trailer is caused to pass. Instead of attaching a Morse key and relay to alternate segments of the circular disc, however, each of five con secutive segments of such a disc are connected at the transmitting end with a key, each key controlling a source of electromotive force, while at the receiving end of the circuit each of five corresponding consecutive segments of a segmental disc or ring is connected with a relay. There are four series of such tively connected keys and relays on the mental discs. One or more of each series of keys may be depressed to form a certain bination of electric impulses representing a given letter, which impulses are transmitted by the trailer over the circuit and in turn these impulses operate a corresponding series of lays at the receiving station. These relays by their armature operate mechanism whereby a desired given letter is selected and printed in page form, As there are four series of keys and relays attached to the segmental discs it will be clear that four letters of four different given words or messages may be transmitted at every revolution of the trailer around the disc. The rate of transmission of words will then depend on the speed of rotation of the trailers, and this in turn is largely controlled by the mechanical and electrical limitations of the apparatus and line. In the Baudot system a keyboard is used to transmit a prearranged combination of electric impulses to form a letter. In the multiplex printing telegraph tem under consideration the messages are transmitted by perforated paper strips, ing a transmitter, somewhat as described herein in the case of the Wheatstone automatic tem. In the multiplex printer the paper is forated by a keyboard perforator manipulated by an operator at a speed slightly greater than that of the automatic transmitter of the printer, and the paper there prepared is fed directly from the perforating machine into the said transmitter. By the foregoing arrangement four uchannelso are provided on one wire and as the wire is duplexed in the manner described herein in connection with the Morse duplex tem the equivalent of eight channels' s obtained on one wire. As each channel may he operated at the rate of 40 words per minute a total of 320 words per minute is thus obtainable in practice on long circuits, the messages being printed in Roman letters on regular telegraph blanks.in page form. Means are provided for the maintenance of exact synchronism between the transmitting and receiving trailers over their respective segmental discs —analogously as in the synchronous multiplex Morse system, but greater refinement of apparatus and oper ation is necessary in the multiplex printer. Obviously this must be so from the fact that in the multiplex printer means are provided for operating the typewriter carriage, printing the letters. etc.