MAGNETIC DRUM TRANSLATOR FOR TOLL SWITCHING OFFICES 719 



Six-digit translations are obtained in a manner similar to that des- 

 cribed above except that the checking network on the relays is switched 

 to check for six rather than three digits. In some instances the decoder 

 must refer to one of the translators in the common pool of "foreign area 

 translators" in order to obtain the reciuired information. Frequently, sev- 

 eral different cards must be dropped successively before a route is finally 

 established for the outgoing call. 



With the above description as a background, we may proceed to discuss 

 the magnetic drum translator. 



THE ANALOGOUS FUNCTIONS OF THE MAGNETIC DRUM TRANSLATOR 



The magnetic drum translator is essentially a device which performs 

 a translation by making a selection from a recurrent pattern of electrical 

 pulses generated by a magnetic drum unit. A schematic diagram of the 

 magnetic drum translator, as arranged for direct substitution for a card 

 translator, is shown in Fig. 4. In this diagram, the system is divided into 

 three principal functional components: (a) the drum memory assembly 

 which produces (from the outputs of 80 reading amplifiers and a timing 

 unit) a repetitive pattern of electrical pulses representing all the transla- 

 tions on the drum, both input codes and corresponding output codes; (b) 

 the translation selecting unit which reads that portion of the pulse pat- 

 tern representing input codes and acts to identify the unique code group 

 which matches the incoming information from the decoder ; (c) the trans- 

 lation delivery unit which, under control of the translation selecting unit, 

 gates-out the particular pulses of the corresponding output code from the 

 continuous stream of microsecond pulses, and converts them into signals 

 capable of operating the register relays in the decoder. 



To maintain direct interchangeability, two items of apparatus were 

 adopted virtually without change from the card translator. These are the 

 (ODE CHECK RELAYS which accept and check input information, and the 

 CHANNEL OUTPUT DETECTORS comprising cold-cathodc gas tubes and as- 

 sociated transformers. This allows input and output terminal facilities 

 to the decoder to be the same for both translators. 



It should be noted that the magnetic drum memory assembly differs 

 significantly in one functional respect from the binful of cards in the card 

 translator. When a selected card is being read by the photo-electric cells 

 in the output channels, no other cards are available. In the drum trans- 

 lator, all translations are continuously available and if a number of trans- 

 lation selecting and translation delivery circuits are employed, all may 

 obtain translations from a common drum memory assembly at the same 

 time without interference. This feature could not be demonstrated in the 



