172 



Hr.l.L SYSTEM Tf.CHXIC.IL JOURX.IL 



fuses in series with the line ami fonniny the blades of a switch. These 

 fuses ha\e been found satisfactory for tiie inf,erruption of voltages as 

 high as 25, 000. Following this fused switch is a l,oOO volt breakdown 

 static spark gap to groinid and a oOO volt breakdown vacuum gap 



■^TRRT^h 



® 



© 



^l^W^h 



TO CAPPlER 



Kig. 21 — Srheniatic of Protertion Circuits 



across the line. l-Oliow ing these there are two series capacity elements 

 which are high Noltage mica condensers. These condensers ha\e a 

 capacity of .007 fit. and a breakdown voltage in excess of 7,oOO. FinalK', 

 there is proxided a rei)eatiiig coil with the mid-point of the line side 



Cftl?l?ICI? FI?E(3UENCV IN KILOCYCLES 



40 W 80 100 lEO 140 IfcO 



Fig. 22 — Change in the Attenuation of the High Frequency Line Necessary to 



Maintain a Constance X'oice Freciuuncy Level with \'ariation in the Frequency of 



the Carrier 



winding groimded and protected 1)\ .j(K) \(ilt \acuiim gaps to groimd. 

 This repeating coil is also provided with a grounded shield between 

 the windings and has a breakdown voltage from the winding to the 

 shiekl of 1,000 volts. The operation of this protective circuit has 

 been demonstrated se\eral limes in the field by connecting one phase 



