536 Mr. Sidney George Brown [March 12, 



There are two kinds of receivers now commonly employed, viz., 

 the siphon recorder and the " drum " cable relay. 



The siphon recorder, invented by Lord Kelvin in 1867, is an 

 instrument that inks the message as received on a moving band of 

 paper. 



The " drum " cable relay, by means of an electric contact-making 

 device, brings in a fresh source of energy from a local battery, so 

 that the electric signalhng impulses are multiphed many times over 

 in power, and are thus enabled to do many useful things besides 

 inking the message, such as working signalling keys to re- transmit 

 the message on to another line, or to guide the levers of an auto- 

 matic punching machine to perforate the message. 



The siphon recorder requires the constant attention of a clerk, 

 the " drum " cable relay does not. 



The siphon recorder consists of a bent glass siphon tube nearly 

 as fine as a human hair. 



The siphon is suspended by a fine bronze wii'e ; one end of the 

 tube dips in a reservoir of blue aniline ink, the other end can move 

 across the surface of a traveUing band of paper, upon which it inks 

 its movement. 



If the end of the siphon touched the paper, the friction thus 

 introduced would be fatal to the proper working of the instrument, 

 because of the loss of sensitiveness ; it is, therefore, kept in a state of 

 constant vibration by attaching the tube near its end by means of a 

 silk fibre to an electro-magnetic vibrator. The message is thus recorded 

 as a close row of ink dots on the moving paper, and the glass tube is 

 quite free to swing sideways under the action of the received signals. 



The siphon tube is joined by two siJk fibres to a rectangular 

 suspended coil, of fine insulated copper wire, which coil hangs in a 

 strong magnetic field. 



The currents from the cable flow through the wire of the 

 suspended coil, and the re-action of these currents with the magnetic 

 field cause the coil to oscillate, to one side or the other, dependent 

 upon the direction of the current. 



The motion of the coil is transmitted by means of the two fibres 

 to the siphon, and thus the signals are recorded as received. 



Ever since the invention of the siphon recorder efforts have been 

 made to turn it into a relay, but two difficulties had to be faced. 

 The extreme feebleness of the received signalling currents was such 

 that they were incapable of opening and closing a battery circuit so 

 as to do useful work in that circuit. 



The reason for this is that a certain force is required to press the 

 relay contacts together to complete the circuit, and a certain force to 

 break the circuit when formed : these forces of " make " and " break " 

 are too great for the cable relay to supply under normal working 

 conditions. 



The second difficulty was the want of definition in the signals 



