Ilil.lil'IIOM: IK.IXSMISSIOX M.IIXriiW'IMIi .11 



iHcasurinn sirts of tin- I-A or '.\-.\ typrs in ((iiiiu-clion willi uiIut m.iiii- 

 tenaiuv work. 



Diu- \cry essi-ntial ri'<iiiiriMm-iit in carr\iiin on a sN>.tiMnatic trstinn 

 (>ro^;rani is to have rt-cords of tlu- di-taili-d inaktup of llu- toll cirriiits 

 which give both the circuit layouts and the (.•(iiiiptncnl associated with 

 the circuits. Such a record is valuaMe. not only in giving the main- 

 tenance forces a i)icture of the circuits and e(|iiipmeiil which they ace 



Fig. 4 — Sample of a Toll Circuit Layout Record Card 



testing, but it also furnishes a means for establishing the transmission 

 standards to which they should work. When transmission tests indi- 

 cate trouble, this record becomes of particidar ser\ice in locating and 

 clearing the cause. 



Fig. 4 shows a sample of the t\pe of toll circuit Uuout record card 

 which has proven very satisfactory and is now generally used in the Bell 

 System. 



Telephone Repeater and Carrier Maintenance. \'oice fre(|ueiu\- 

 telephone rei^eaters were discussed in a paper b\- Messrs. (".herardi 

 and Jewetf^ and carrier systems in a paper by Messrs. ("olpitts and 

 Blackwell.* The various arrangements of amplifiers to provide for 

 telephone repeater and for carrier operation as described in these 

 papers tnake up integral parts of toll circuits and introduce elements 



'Gherardl and Jpwett, "Telephone Kei)eaters," Transactions of A. I. !•'.. E., 

 IQ19, Vol. X.W III, l>art 2, pps. 1287 to U45. 



'Colpitts and Blackwell, "Carrier Current Telephony and Telegraphy," Tnins- 

 actions oj A. I. E. £.. 1921, Vol. XL, pps. 205 to 300. 



