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BELL SYSTEM TECHNICAL JOURNAL 



the low frequency cut-off c^iused by them hes well below the low 

 freq^iency cut-off of the horn, an inappreciable error is introduced in 



Fig. 15 — Diagrammatic sketch of the mechanical system of the phonograph 



using for design purposes formulas of low pass filters^-. The two for- 

 mulas which will be used are as follows: 



TT \ nic 



(12) 



Where 

 f^ = cut-off frequency of a lumped transmission system in cycles 



per second 

 c = shunt compliance per section in centimeters per dynes 

 m = series mass per section in grams 



^ 



(13) 



where Zo^^ is the value of characteristic impedance over the greater 

 part of the band range. 



'-Campbell, G. A., "On loaded lines in Telephonic Transmission," Phil. Mag., 

 March, 1903. , ^^ . 



" So may be called nominal mid-shunt or mid-series impedance. 1 heir actual 

 values in the transmission band being at any frequency/.. 



lid-series =2.o\l— (^) 



Je ' 



mid-shunt = 



V.-(i)' 



