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BELL SYSTEM TECHNICAL JOURNAL 



The circuit of one element of the modulator for producing low- 

 frequency beats is shown in Fig. 19. The input circuits A and B 

 are supplied from oscillator No. 4 and one of the other three, respec- 

 tively. The plate circuit includes the windings of a balanced relay 



C- CLOCK. 



SMG- SUBMULTIPLE GENERATOR. 



S- SPECIAL THREE-WAY SWITCH. 



0i,02,03- OSCILLATOR 100.000.0 CYCLES. 



O4- OSCILLATOR 100,000.1 CYCLES. 

 BFI- BEAT FREQUENCY INDICATOR. 

 R-BEAT RECORDER. 



Fig. 18 — Schematic of complete frequency standard system. 



which makes a contact once for each cycle difference between the 

 input frequencies at A and B and which operates the recording 

 mechanism accordingly. 



I|lh-^h' 



u 



mt 



xrr 



Fig. 19 — Balanced modulator of beat frequency indicator. 



The beat recorder is a counter arranged to count these relay 

 operations for a definite time interval, in this case for 1,000 seconds, 

 and then to print the total and reset to zero. Five such units are 

 provided which print on a wide strip of paper similar to that used in 



