THE BELL SYSTEM 



TECHNICAL JOURNAL 



VOLUME XXXVI NOVEMBER 1957 number 6 



Copyright 1967, American Telephone and Telegraph Company 



A New Storage Element Suitable for 



Large-Sized Memory Arrays — 



The Twistor 



By ANDREW H. BOBECK 



Three methods have been developed for storing information in a coinci- 

 dent-current manner on magnetic wire. The resulting memory cells have 

 been collectively named the "twistor". Two of these methods utilize the strain 

 sensitivity of magnetic materials and are related to the century old Wertheim 

 or Wiedeynann effects; the third utilizes the favorable geometry of a wire. 



The effect of an applied torsion on a magnetic wire is to shift the preferred 

 direction of magnetization into a helical path inclined at an angle of 1^5° 

 with respect to the axis. The coincidence of a circular and a longitudinal 

 magnetic field inserts information into this wire in the form of a polarized 

 helical magnetization. In addition, the magnetic wire itself may be used as 

 a sensing means with a resultant favorable increase in available signal since 

 the lines of flu.v wrap the magnetic wire many times. Equations concerning 

 the switching performance of a twistor are derived. 



An experimental transistor-driven, 330-bit twistor array has been built. 

 The possibility of applying weaving techniques to future arrays makes the 

 twistor approach appear economically attractive. 



I. IXTUODUCTION 



A century ago Wiedemann^ observed that if a suitable magnetic rod 

 which carries a current is magnetized bj^ an external axial field, a twist 



1319 



