6 BELL SYSTEM TECHNICAL JOURNAL 



to the design of measuring systems and the recently developed arrange- 

 ments are therefore better coordinated with other faciHties than those 

 which they replace. A few examples will be given to illustrate the 

 recent advances in transmission measuring work. 



Fig. 3 — Transmission measuring set dev^eloped about 1920 and associated genera- 

 tor as used at a switchboard in testing cord circuits or interoffice trunks. Both units 

 are required for either sending or receiving. 



Figure 3 shows the testing power generator and measuring set 

 developed about 1920 for use in the local plant to measure central 

 ofifi.ce equipment and interoffice trunks with testing power of a single 

 frequency, the frequency employed usually being 1000 cycles. When 



