ELECTKICAL TESTS .1X1) TIU.IR AI'TI.ICATIOXS .Wl 



l),ilaiux'" niotluMls and tin- otIuT "\isii,il" methods, tliat is, ,in .im- 

 plitiiT and di-ttvlor arraii.m'int.'nt. 



Fig. 24 shows the schiMuatir ririniit arranvifim-nt for an oar lial- 



anro ti>st set ami Fig. 2"), that for a .set employing visual methods. 



I'ig. 24 



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Fig. 25 



A description of this apparatus and its de\clopmeni has been gi\cn 

 in a pafXT In- Best.- In brief, one subscriber's set of the circuit in 

 Fig. 23 has been replaced by an oscillator while the other subscriber's 

 set has been replaced b>' a receiver and resistance arrangement in the 

 circuit of Fig. 24 and by an amplifier and detector in the circuit of 

 Fig. 25. The artificial cable of Fig. 23 has also been replaced by dis- 

 tortionless resistance network standards in Figs. 24 and 25. \^arious 

 resistances and coils are also provideti to meet practical testing re- 

 quirements such as adjusting the measuring current, and reducing 

 retlection losses. 



For field testing work, the cimiiis shown in I'igs. 24 and 25 are 

 mounted in compact form in portable boxes which can be readily 

 carried from office to office or wherever required. Portable oscillators 

 for supplying the measuring current are also pro\ided so tliai rom- 



' F. H. Best. Jour. .1. /. E. E., Vol. XI. III. No. 2., Fel)., 1924. 



