THE DU BOIS KEY 



I 1 



on the brass plate d, which is connected by the strip of copper e to the 

 second binding screw b. When interposed in the course of a circuit, 

 the circuit will only be closed when c is depressed to lie in contact 



with d. 



DU BOIS-REYMOND'S FRICTION KEY (figs. 14 and 15) consists 

 of two metal blocks a and b (fig. 14), each carrying two binding 

 screws, fixed on an insulating base. The two blocks can be connected 



Inst. Co. Ltd. Umb, 

 FlGS. 11 AND 15. — TWO FORMS OF THE Du BoiS KEY. 



by a metal cross-bar c, which thus closes the key. This key is of very 

 great service, and is employed in two ways indicated in the two ac- 

 companying figures (16 and 17), where it is represented as being used 

 in the secondary circuit of an inductorium. In fig. 16 is shown the 



Fig. 16. — Plan of the Arrangement of Fig. 17. — Arranged as a Simple Break 

 the Do Bois Key as a Short-cir- Key. Not to re used after this 



cutting Key. Method in a Secondary Circuit. 



arrangement in which it is used as a short-circuiting key. The two 

 terminals of the secondary coil are connected by wires to two of the 

 binding screws on the blocks, one to each block, and to the remaining 

 two binding screws are connected the wires of a pair of electrodes, e, 



