Williams tube
Two alternatives to the delay line, the Williams tube and Selectron tube, originated in 1946, both using electron beams in glass tubes as means of storage. Using cathode ray tubes, Fred Williams invented the Williams tube, which was the first random-access computer memory. The Williams tube was more capacious than the Selectron tube (the Selectron was limited to 256 bits, while the Williams tube could store thousands) and less expensive. The Williams tube was nevertheless frustratingly sensitive to environmental disturbances.