30O 



BELL SYSTEM TECHNICAL JOURNAL 



During the recent war a rapid automatic method was de\eloped 

 for varying the tuning of a circuit in such an analyzer in connection 

 with the analysis of sounds radiated by submarines. The anaKzer 

 described in this paper is in principle the same as this apparatus 

 but includes such impro\ements as were found desirable b\' experience 

 to increase the speed, dependability and convenience of use. The 

 present apparatus is capable of recording the frequency and mag- 

 nitude of each component in a complex wave between 20 and 1250 



Fig. l^Schcnialio .Analyzer Circuit 



cycles or 80 and 5000 cycles in about five niiniiics. This analyzer 

 does not measure the phase of the various components but has the 

 advantage that the frequencies need not be simple multiples of the 

 fundamental as is the case with graphical analyzers. With this 

 apparatus it is possible to measure cjuile accurately component 

 frequencies as close together as about fifteen cycles at the lower end 

 of the range and about 200 cycles at the upper end of the range, and 

 to detect components as close together as three to five cycles at the 

 lower end and fifty cycles at the upper end of the range. 



rKiNciiM.ics ()!■ ()i'i:K.\ri()\ oi' Till'. .\^Al^vl■.R 



Fig. 1 is a schematic diagram of the essential elements of the 

 analyzer circuit. The wave to be analyzed is introduced at the 

 input terminals from which it passes to an input equalizing network 

 and to the variable tuned circuit. The tuned circuit consists of a 

 variable condenser of cajKicitance C and a coil whose inductance 

 is L and resistance R. The value of the capacitance C is \'aried in 

 small steps by an automatic device to be described in the next section. 

 The inductance £, consists of four identical windings on a toroidal 



