THE LOCALISATION OF BREAKS AND FAULTS. 



489 



graph Companies, devised a form of key conveniently suited for 

 this important test (Figs. 272 and 273). In this key there are 

 two blades or levers attached to separate handles moving in an 

 up and down direction. The right-hand or charge key makes 

 contact with plates at the back, which in one position connects 

 the condenser to slides (for charge), and in the other earths the 

 condenser. The left-hand or discharge key in one position earths 



Fig. 273.— Plan of Saunder's Key. 



the galvanometer (for discharging the line and condenser pre- 

 vious to a test or for taking the absorption discharge) and in 

 the other completes the circuit of the galvanocneter key. 



By means of an ebonite rocking bar under the handles (seen 

 in the illustration) it is impossible for both keys to be down at 

 once, thus preventing too great a charge through the condenser 

 and galvanometer, and also providing that the absorption dis- 



