HISTORY AND PROGRESS. 145 



The remaining terminals, T, i, n, n, &c., are for the connec- 

 tions between the two slabs. 



The following are the different positions of the commu- 

 tators, &c., for different uses of the apparatus : 



1. THE APPARATUS AS TERMINAL STATION. 



POSITION I. 



Both translation commutators are stoppered at S. Both current 

 commutators are at 1. Contact cones in both the circuit-breakers. 



A) Apparatus I. (left] receives signals. 



The current coming from Z t passes through the screw, Z,, the 

 galvanoscope (1, B P 2), the translating commutator, c,, contact 

 cone in S, key (1, D P 4), galvanoscope BJ current commutator 

 (1, p,, 3), relay (1, G P 2), current commutator (2, F P 4), screw Z, 

 circuit-breaker, M n screwZ', and earth, and through the earth back 

 to the battery of the sending station. 



The tongue of the relay, 'G P is attracted against the metal 

 contact point, and the local circuit closed as follows : 



Local Battery (Z t i, C7), the screw, A, of the printing instru- 

 ment, a, through the releasing magnet, b, at the same time 

 through both coils of printing magnet, , to the relay, A, 

 tongue, metal contact, , and back to the Z of the local 

 battery. 



Thereupon both the magnets of the instrument are made to 

 attract ; the releasing magnet sets the clockwork in motion, and 

 the printing lever of the other magnet is held down until an 

 opposite current coming from L l repels the tongue of the relay from 

 the metal contact. 



.5) The Apparatus I. is made to transmit signals. 



The key D l is drawn sideways, so that the spring * a is pressed 

 against the contact, 2. The counteracting battery, K, is then in 

 circuit as follows : 



(Z, K, C) Z, MJ, E, earth, opposite station apparatus, Z p 

 lightning guard A, Apparatus I. (1, B,, 2), (C,, ), (1, D,, 

 *g, 2), back to the battery, K. 



A negative current, therefore, passes through the line and the 



L 



