AUTOMATIC TESTING OF INTERTOLL TRUNKS 935 



trunks to save time. The circuits are arranged so that, if desired, the Tele- 

 typewriter may print a record of busy trunks passed over without test. 

 By means of a timing key this record can be delayed two minutes or four 

 minutes to wait for the trunk to become idle. This is used when it is 

 preferable to wait a reasonable time for trunks to become idle to secure 

 tests on a larger proportion of the trunks. 



Trunk Classes 



A class relay, operated by a contact on the test connector crosspoint 

 as previously mentioned, indicates to the test frame the type of trunk 

 being tested so that it can properly handle the test call. There are 33 of 

 these relays. A flexible cross-connection in the path of the class contact 

 on each test connector crosspoint permits each crosspoint to be assigned 

 to the particular one of the 33 class relays which represent the charac- 

 teristics of the intertoll trunk associated with that crosspoint. Twenty- 

 eight of the class relays are used in connection with trunks on which auto- 

 matic transmission tests are made and indicate, among other things, the 

 specified loss of the trunk being tested. These relays are provided in such 

 a manner that, for any trunk, a class can be chosen w^hich agrees with the 

 specified loss of the trunk to within ±0.1 db over the range 3.8 db to 12.1 

 db. The specified loss is used by the automatic transmission test and 

 control circuit when computing the deviation of the measured loss from 

 the specified value, as covered later. 



Test Cycles 



The test frame may be set up by means of control keys to perform 

 ^'arious kinds of test cycles. Some of these test cycles, are described 

 briefly below. 



Code 103 Tests. A complete check is made of all the circuit operating 

 features including the ringing and the supervisory features while the 

 connection is established. If this test is passed successfully, one may 

 assume that the intertoll trunk circuit and the associated signaling chan- 

 nel will properly handle normal calls although this does not prove that 

 the transmission performance is satisfactory. 



Signaling Channel Tests. This is an abbreviated code 103 test to verify 

 the integrity of the trunk and its signaling channel. It can be made quite 

 rapidly and is useful for checking the correctness of patching after daj'' 

 and night circuit layout changes. 



Pass Idle Test. This is a test cycle which may be I'un occasionally 

 during a very light load period to detect trunks which may l)e falsely 

 busy. 



