CARD TRANSLATOR FOR NATIONWIDE DIALING 1071 



It comprises a flat metallic plate upon which the card is laid, two rails 

 which are insulated from the plate and project about it an amount 

 equal to the thickness of the stock from which the cards are made plus 

 the allowable amount of out-of-flatness and a metallic roller that is 

 sufficiently long to span the rails. The rails and the flat plate are ele- 

 ments of a neon tube detection circuit which is arranged so that if the 

 roller in passing over the card contacts it the tube will fire. If it does not 

 fire, the card is within the flatness setting of the gauge. 



To meet the 0.012" allowance consistently it was necesary to resort 

 to special stress relief annealing. In developing the process it was found 

 that the cards have to be degreased thoroughly and a clean condition 

 has to be maintained at all times. The cards are clamped under heavy 

 pressure between thick nickel plated plattens and are then heated and 



Fig. 23 — Card flatness gauge. 



later cooled in a reducing atmosphere. Such a procedure would seem to 

 be reasonably straightforward, but it was found that the heating cycle 

 has to be controlled precisely as otherwise the surface is roughened. 



Smoothness of the cards was found to be related to surface color. 

 Improperly stress relief annealed cards usually assume hues of blue and 

 brown which were traced to surface films of so little thickness — perhaps 

 in the order of 500 to 1000 Angstrom units as to cause interference col- 

 ors. It was found that when the surfaces are discolored excessively, there 

 often is an appreciable increase in interface friction, sometimes amount- 

 ing to 30 per cent. This is undesirable because free action of the cards is 

 of paramount importance and of course, wear should be minimized. It 



