248 



THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1951 



set are shown on Fig. 7 which also illustrates the effect of the equalizer. 

 Overall air-to-air frequency responses of the two types of set are shown 

 on Fig. 8 for long and short loops. The broader frequency range and the 

 notable reduction in spread between long-and short-loop performance are 

 evident. 



Subsidiary but essential transmission features of the new set include a 

 copper oxide click reducer across the receiver particularly desirable for a re- 

 ceiver of such high efficiency; low susceptance to power interference on party 

 lines by the high impedance of the ringer and by shaping the receiver re- 

 sponse below 300 cycles;^ and effective suppression of dialing interference 



LOOP RESISTANCE IN OHMS 

 500 600 700 800 900 



1000 



UJ 

 (O 



UJ 



a. 



-20 



500 TYPE SET 

 ■500 TYPE SET 



(NO EQUALIZER) 

 ■302 TYPE SET 



1100 1200 1300 



J 



4000 6000 8000 10,000 12,000 



LENGTH IN FEET (nO.26 GAUGE LOOP) 



Fig. 7 — Relative volume levels. 



14,000 16,000 



with radio and television reception by a small capacitance and resistance 

 associated with the inductance of the line winding of the induction coil. The 

 integrated design employed assures these features at minimum cost. 



Dialing 



A controlling limitation on dialing range is to be found in the degree to 

 which the pulse characteristics vary from the optimum value from dial to 

 dial and from time to time over the period of service. The new dial design 

 by better governing and cam control of the individual pulse form provides 

 the required improvement in loop range by assuring much better uni- 

 formity in every respect. 



Service experience has shown that the better visibility and greater con- 



