MAGNETIC DRUM TRANSLATOR FOR TOLL SWITCHING OFFICES 711 



past one or more heads used for writing or reading digital data. Usually, 

 as in the translator, the same head is used for both functions. In most 

 drum-system designs the pole-tips of the heads are close to the recording 

 surface but do not touch it, and the heads themselves bear a resemblance 

 to those used in conventional magnetic sound recording, giving therefore, 

 a "longitudinal" polarization to the medium as sketched diagrammati- 

 cally in Fig. 2. There is very little further resemblance to sound record- 

 ing, since digital information is stored in a binary or two-valued code 

 which, on the translator drum, is represented by the two possible polari- 

 ties of saturation of the magnetic medium. To one of these polarities is 

 assigned the code value "O," and this condition prevails except where 

 the opposite polarity is inserted to represent the code value " 1." 



It should be mentioned that several other systems have been devised 

 which employ the two directions of saturation, sometimes accompanied 

 by a general background of magnetic neutrality, to effect a greater con- 

 centration of digital information than that used in the translator. Systems 

 other than the one chosen for this application were, for the most part, 

 considered to be less reliable. 



THIN MAGNETIC 

 COATING 



SIMPLIFIED 

 WRITING AMPLIFIER 



READING AMPLIFIER 



r" 



THRESHOLD 

 LINEAR OUTPUT 



AMPLIFIER STAGE 



•^ V 



MONITOR 



D 



OUTPUT 



L. 



MAGNETIC READING 

 AND WRITING HEAD 



Fig. 2 — Simplified diagram of magnetic drum digital data storagje system. 



