AUTOMATIC TESTING OF INTERTOLL TRUNKS 937 



verify the trouble condition. He notes the nature of the trouble from 

 the progress and trouble indicating lamps and then causes the test 

 frame to resume testing by advancing it to the next trunk with a manual 

 advance key. 



When the associated Teletypewriter is provided and operating, it is not 

 always necessary to sound an alarm and thus interrupt the regular work 

 of the attendant. Instead the Teletypewriter may print a trouble record. 

 For this purpose troubles are grouped into 18 categories. When a trouble 

 is detected, the Teletypewriter prints a record of the trunk identification 

 number together with a letter in a separate column indicating one of 

 these categories. The test frame then usually makes a repeat test on the 

 same trunk to verify the trouble except when the connection must be 

 held, as discussed later. If the second test is satisfactory, the trouble was 

 of a transient nature and the test frame resumes testing, leaving a single 

 line trouble record on the Teletype tape. If the trouble is still present on 

 the second trial, a second record is printed on the next line for the same 

 trunk. 



If the nature of the trouble, as indicated by its category, is such as to 

 render the trunk unfit for service, the test frame will stop after the second 

 trial, hold the trunk busy, and sound an alarm to attract the immediate 

 attention of the attendant. If, however, the trouble is of a minor nature 

 that can be tolerated temporarily, the test frame advances automatically 

 to the next trunk after the second record is printed, and resumes testing 

 without sounding an alarm. By periodic inspection of the Teletype record 

 the attendant can note those trunks needing maintenance attention by 

 means of the double line trouble records. A test cycle can thus be com- 

 pleted with the minimum of supervision on the part of the attendant. 



When the nature of a trouble is such that its identity is likely to be 

 lost if the original connection is broken down, e.g., failure of a holding 

 ground, the test frame will not attempt a second trial but stop, hold the 

 trunk busy, and sound an alarm. Failure to complete a transmission test 

 satisfactorily is included in this class because such failures can be due 

 to the testing equipment itself. 



AUTOMATIC TRANSMISSION TESTS 



Basic Scheme of Measurement 



An automatic transmission loss measurement consists essentially of 

 adjusting the loss of a pad at the receiving end of the trunk to bring the 

 test power level at the pad output to a fixed value. A functional diagram 

 of the arrangement is shown in Fig. 4. 



