928 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1956 



testing the operational (signaling and supervisory) functions of dial-type 

 intertoU trunks, and of making two-way transmission loss measurements 

 and a noise check at each end. The test results may be recorded at the 

 originating end by means of a Teletypewriter. 



Automatic trunk testing has been used for many years in the local 

 plant for checking the signaling and supervisory features of interoffice 

 trunks. The automatic intertoll trunk testing equipment serves a similar 

 function with respect to these operational features of the intertoll trunks. 

 Because published material is available on automatic operational test- 

 ing,* these features will not be discussed in detail in this paper; more 

 emphasis is given to the transmission testing features which are new. 



MAINTENANCE ARRANGEMENTS FOR INTERTOLL TRUNKS 



Except in the very small offices, intertoll trunks usually have a test 

 jack appearance in the toll testboard for maintenance purposes. Cord 

 ended testing equipment in the toll testboard positions enables the 

 attendants to perform various operational tests and to make transmis- 

 sion loss, balance, noise or crosstalk measurements. Facilities are pro- 

 vided for communication with distant offices and with intermediate 

 points where carrier or repeater equipment may be located. Testing of 

 carrier or repeater equipment as individual components or systems is 

 an important aspect of the trunk maintenance problem but is beyond 

 the scope of the present paper. 



The maintenance of intertoll trunk net losses close to their specified 

 values is currently a most important transmission problem. Various 

 aspects of the problem are discussed in a companion paper, f 



Although the manual testing equipment mentioned above is vital to 

 trunk net loss maintenance, the need for reduction in time and effort 

 required to make measurements has led to the provision of semi-auto- 

 matic testing arrangements. These arrangements permit a testboard 

 attendant to check transmission in the incoming direction by dialing 

 code 102 over a trunk. The trunk is connected to a source of one milli- 

 watt test power at the far end and a measurement of the received power 

 indicates the net loss. The equivalent of a semi-automatic two-way test 

 may be obtained by making a code 102 test in each direction. If com- 

 plete information on the test results is desired by one testboard at- 

 tendant, the attendant at the other end of the trunk must report back 

 his results. 



* R. C. Nance, Automatic Intertoll Trunk Testing, Bell Labs. Record, Dec, 

 1954. 



t H. H. Felder and E. N. Little, Intertoll Trunk Net Loss Maintenance Under 

 Operator Distance and Direct Distance Dialing, page 955 of this issue. 



