932 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1954 



separations over which a prescribed degree of linearity can be obtained. 

 It can be shown that the maximum range of linearity is obtained with 

 {KQY = 2 and that the center of this range is at a: = 3^. Fig. 5 is a graph 

 of (5) against x with {KQY set at 2, 



SCANNING CIRCUIT 



The scanning circuit is a high speed electronic switching and detecting 

 device which lapidly selects successive contacts, checks whether the 

 contact is opened or closed, and displays this information on the vertical 

 plates of the scope. Each contact is assigned a particular vertical refer- 

 ence level. When gauging, each level appears as a horizontal line with a 

 vertical step on the line indicating the armature position for the contact 

 operation. 



Electron tubes designated "C" on Fig. 6 serve as switches to connect 

 one contact at a time to the vertical plates of the scope. Each contact is 

 connected to the grid circuit of a C tube. In order to test a contact its 



5 

 UJ 0.5 



0.3 



0.2 



0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 



X=d/d' 



Fig. 5 — Curve showing E IE max versus x with (KQ)^ = 2 computed from equa- 

 tion (5). 



