XI. APPLICATIONS. 309 



This instrument is so well known as scarcely to need description, being 

 used in almost every country ; its advantage over the Morse embosser consists 

 in the greater legibility of the signals, which can be read in any light, and it 

 requires much less power to work it. This form is used on lines of moderate 

 length, where the direct line current is sufficient to actuate the electro-magnet 

 without the assistance of a relay and local battery. 



1558a. Model of a Morse Printing Telegraph (blue 

 writer), with key, galvanometer, and paper stands. 



A. Herbst, Berlin. 



1559. Siemens' Local Ink-Writer. 



Used in connexion with a relay and local battery on lines where the direct 

 current is not sufficiently strong to actuate the direct ink-writer. 



1560. Single Needle Instrument. 



Used on lines of a class superior to those on which Wheatstone's A B C is 

 employed. It is but little liable to derangement, and requiring no adjustment 

 is preferred to recording or acoustic apparatus for this class of circuit. 



It is more trustworthy than the earlier instruments of its kind, on account 

 of the steel magnetic needle inside the coil being superseded by one of soft 

 iron magnetised by induction from a permanent magnet, so that the incon- 

 venience formerly experienced by the needle losing its magnetism is 

 prevented. 



A modified construction of Highton's pedal key is adopted instead of the 

 drop handle of the earlier instruments. 



1561. Wheatstone's ABC Instrument, Communicator, 

 and Indicator. 



This instrument is much used on wires leased to private persons, and for 

 short postal lines, either with or without intermediate stations. It is pecu- 

 liarly well adapted for these purposes on account of not requiring skilled 

 labour for its manipulation. The instrument being worked by a magno- 

 electric machine within the instrument, batteries are not required. 



Switches used with this instrument. 



Alarum 



1562. Double Current Morse Key. 



This has superseded the wheel key formerly used It can be arranged 

 either to be worked as a single current Morse key, or to send double currents, 

 as desired. 



1563. Stroh's Polarised Belay, with Inducing Magnet. 



This relay is similar in construction to the electrical portion of the Wheat- 

 stone " Receiver." It consists of two upright electro-magnetic bobbins 

 placed side by side ; two horizontal pieces or tongues of soft iron are fixed at 

 their ends on a vertical axle ; their other ends play between the pole pieces 

 with which the cores of the bobbins are provided. The adjustment is effected 

 by a spiral spring. 



1564. New form of Non-polarised Belay. Post Office 

 pattern. 



This consists of two vertical electro-magnetic bobbins the cores of which are 

 prolonged. Two soft iron needles are fixed on a vertical axle passing between 

 the coils, one at the top and one at the bottom end of the axle. These 

 needles are placed crosswise, so that when the cores are rendered magnetic the 

 four poles of the bobbins tend to turn the needles on their vertical axis in the 



