The choice of the main type of memory used in the TXE2 (and the TXE4) was particularly characteristic of the general design philosophy, that the components used had to be of a technology that had been tested over many years. The choice thus went to the 'Dimond ring' type of memory, named after T. L. Dimond of Bell Laboratories, who invented in 1945. They were large-diameter magnetic ferrite toroidal rings with solenoid windings, through which are threaded writing and reading wires. These racks gave the ability to convert a subscriber's directory number into an equipment location identity. This was a considerable innovation in British exchanges since in Strowger exchanges the directory and equipment numbers had to be the same.