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BELL SYSTEM TECHNICAL JOURNAL 



recorder at the right. Directly above the recording meter is the re- 

 ceiving panel which amplifies and rectifies the current received from 

 the line. The tuned circuit associated with the frequency marking 

 device is mounted on the rear of the panel below the meter. 



The recording meter is a new design developed by the Weston Elec- 

 trical Instrument Corporation in accordance with specifications drawn 



Fig. 2 — Experimental setup of recording system. 



up by Bell System engineers to meet the special needs of telephone 

 circuit testing. It is extremely fast in operation, the moving system 

 responding to fluctuating currents in about the same manner as the 

 moving system of a fast d-c. voltmeter. Complete transmission fre- 

 quency runs on circuits may be made in as short a time as one minute 

 when the transmission loss is changing rapidly with frequency and 

 in much less time with less rapid transmission loss variations. The 

 ballistics of the moving system are such that the recorder may be used 

 as a recording volume indicator although for this purpose the readings 

 at some parts of the scale are not exactly the same as those of the non- 



