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inductance. As these panels are all of the same size, it is possible if 

 necessary to change radically the arrangement of the interstage net- 

 works, or substitute entirely different ones without any difficult 

 mechanical work on the amplifier. Each of the condensers and 

 resistances is contained in an earthed metal box, into which it is sealed 

 by a wax insulating compound. The frame in which the panels are 



Fig. 3. 



mounted is earthed and metallic fins are provided between the various 

 panels in such a manner that any current which leaks through a film 

 of moisture which might be deposited on the surface of the panels 

 must pass to earth. The plan of mounting each individual piece of 

 apparatus in a metal box, and sealing it in with insulating compound, 

 has been adhered to throughout, the tubes, meters and switches of 

 course being excepted. This is principally for protection from the 

 serious humidity frequently found in cable stations. Additional 

 protection is provided by electric heaters drawing current from the 

 battery which operates the filaments of the vacuum tubes. Frame- 



