AUTOMATIC TESTING OF INTERTOLL TRUNKS 931 



the test call and making operational tests on the intertoll trunks. For 

 automatic transmission tests an automatic transmission test and control 

 circuit, provided in a separate frame as an adjunct to the test frame, is 

 brought into play. A Teletypewriter, mounted in the transmission test 

 frame, is adapted for use with the equipment in the originating office for 

 recording test results. The Teletypewriter is used to make a record of 

 trunks having some defect in their operational features, busy trunks 

 passed over without test and, during transmission tests, to record the 

 results of the transmission measurements. The test frame and associated 

 transmission test and control circuit and Teletypewriter are used prin- 

 cipally by the toll test board forces and, therefore, are usually located 

 near the toll test board. Figure 3 shows such an installation. 



The intertoll trunk test connector frames in the originating office, not 

 shown in Fig. 3, are frames of crossbar switches and there may be several 

 such frames in a large office. Each crosspoint on the switches of the test 

 connector frames represents an individual intertoll trunk. When a trunk 

 is to be tested, the test frame closes the crosspoint of the test connector 

 switches which serves that particular trunk. This extends the selecting 

 leads (trunk sleeve and select magnet leads) of the trunk to the test 

 frame for use in setting up the call. A class contact on the test connector 

 crosspoint also operates one of several class relays in the test frame when 

 the crosspoint is closed. The function of the class relay is discussed later. 



The test frame has an appearance on the incoming link frame of the 

 office switching train. The intertoll trunks to be tested appear on the 

 outgoing link frames of the office switching train. When a trunk is to be 

 tested, the test frame engages the office common control equipment (de- 

 coder and marker) , through a connector, and requests a path between the 

 test frame appearance on the incoming link frame and the particular in- 

 tertoll trunk which is to be tested. The common control ecjuipment is 

 able to set up this path since the test frame has closed a test connector 

 cross-point to bring the selecting leads of the trunk to be tested into the 

 test frame. The common control equipment uses the select magnet lead 

 to identify the trunk to l)e tested and thus is able to set up the path to 

 that particular trunk. The test frame uses the trunk sleeve lead for busy 

 test purposes and for controlling the test call. 



In the distant offices separate groups of test lines provide automatic 

 test terminations for operational and transmission tests, respectively. 

 These are reached through the switching train as indicated in Fig. 2. The 

 three digit service code 103 is reserved in toll switching offices for i-each- 

 ing the operational test lines and code 104 is reserved for reaching the 

 transmission test lines. A transmission measuring and noise checking 



