98 THE ELECTRIC TELEGRAPH. 



lines is to be used. When the apparatus ' at the inter- 

 mediate station is to correspond with a station on the right, 

 whilst the line on the left remains in circuit with the 

 board, holes 2, 4, and 7 are provided with pegs. If the 

 intermediate station now works the key, currents circulate 

 from the c-pole of the battery through 1, lever of key, 3, 

 earth ; and from the z-pole to R O , through the peg in hole 4, 

 L, G 2 , to the line on the right. In receiving signals from 

 the same side the key remains at rest, the currents arriving 

 pass over G 2 , L, peg 4, R O , 2, coils of relay, ,1, R U , peg 7, T, 

 back contact of key, 2, 3, earth, &c. 



During both transmission to and reception from the 

 station on the right-hand side, if a current arrive from the 

 opposite direction, it must pass through the coils of the 

 galvanoscope G L (deflecting the pointer), over peg 2, to earth. 

 The deflection of the galvanoscope pointer is observed by 

 the employe, who takes his measures accordingly. 



When the reverse is to take place, that is to say, the 

 intermediate station is to correspond with a station lying to 

 the left, whilst that on the right remains in circuit with the 

 galvanoscope, the pegs are inserted in holes, 1, 7, and 5. 

 The signals given by the key take the following road : z, of 

 battery, R O , peg 1, L, G L , to line on the left, apparatus at the 

 opposite station, and earth, and from the c-pole of the 

 battery to 1, lever of key, 3, earth. Arriving currents from 

 the same direction come over G lt L, peg 1, R , 2, coils of relay, 

 1, RU, peg 7, T, key, 2, 3, earth. 



Those arriving from the other side deflect the pointer of 

 G 2 , and to pass to earth by G 2 , .L, peg 5, earth. 



In both cases the employes have to pay attention to the 

 galvanoscope, as in cases of emergency it is sometimes 

 necessary to postpone the transmission or reception of a 

 message on one line until the more pressing one from the 

 other side has been disposed of. 



67. Siemens and Halske's Intermediate Station Commuta- 

 tor. The commutator represented in perspective in Fig. 52 

 is much simpler in construction than that of Nottebohm, 

 and answers all the requirements of an intermediate station 



