Dimond ring

A Dimond ring or Dimond ring translator was an early type of computer memory, created in the early 1940s by T. L. Dimond at Bell Laboratories for Bell's #5 Crossbar Switch, a type of early telephone switch.

Structure
Large-diameter magnetic ferrite toroidal rings with solenoid windings, through which are threaded writing and reading wires.

Uses
It was used in the #5 Crossbar Switch and TXE (prior to version 4) telephone exchanges.