AUTOMATIC TESTING IN TELEPHONE MANUFACTURE 1135 



device that will do the required job and that can be put in use in time 

 for early production. Once the facility is in use it may be starting on a 

 productive life that will run thirt}^ years or longer. The designer may 

 think of countless ways to improve it or to redesign it completely. If his 

 improvements or redesign can be proved in on a business basis, they may 

 be undertaken. Sometimes the}^ cannot be proved in. The evolution that 

 has taken place in test set designs has been possible mainly because the 

 customers have wanted newer products, or products delivered at a greater 

 rate. Advancement has been attained under a compulsion to take each 

 step ciuickly and siu'ely. This has represented a real and continuing chal- 

 lenge to the test engineering force. 



With these general considerations in mind the author has chosen three 

 automatic testing devices of diverse character to discuss in some detail. 

 The associated papers^' ^ cover additional machines. The machines de- 

 scribed illustrate in various ways the principles discussed above. 



THE NETWORK TESTING MACHINE AT INDIANAPOLIS^ 



The 425B network^^ is used in the 500 series telephone sets to furnish 

 the transmission link between the handset and the line. Its shop testing 

 requires three tests for transmission, three for capacitance tolerance, 

 three for leakage current, two for ac dielectric strength, one for dc dielec- 

 tric strength and four for continuity. The rotating turret type test ma- 

 chine (Figs. 1 and 2) performs all these tests, applies a conditioning 

 "burnout" voltage and counts and date stamps the good networks. 

 Rejects from each test position are segregated in roller conveyors. 

 In the rotation of the turret an empty test fixture is presented to the 

 operator every 3^^ seconds moving from left to right. She must load each 

 position, taking networks from the pans at her right; good networks, 

 ejected automatically in a roller chute at the left, are hand loaded into 

 the carriage fixtures of the overhead storage type conveyor, which pass 

 within easy reach of the operator's left hand. The pans at the left are 

 used to store good networks when the accessible fixtures of the overhead 

 conveyor are full. The twelve roller conveyors for rejected networks are 

 arranged along the sides of the machine, six on each side. 



The turret contains forty test fixtures (Fig. 3 and 4) and the machine 

 forty positions. The turret rotates continuously, causing eleven contact 

 brushes associated with each fixture to pass against fixed commutator 

 segments and a ground ring associated with the test positions. As each 

 fixture advances past one test position a gear connected cam shaft rotates 

 through a complete cycle. Seventeen switches are operated by the cams 



