A memory technology in some of the earliest computers that used an acoustic delay line. For example, in the 1940s and 1950s, the memory in the EDVAC, EDSAC and UNIVAC I was made of tubes of liquid mercury that were several feet long. Electrical pulses were converted to sound and back to electrical in a continuous loop. Sound Travels Slower than Electricity At one end of the tube, a transducer converted the electrical pulses to sound, which propagated through the mercury to the other end. At that point, another transducer converted the sound to electricity and sent it back to the beginning. The conversion to sound, which propagates much slower than electricity, slowed down the digital data a fraction of a second and caused the device to function as storage. See delay line, EDVAC, EDSAC, UNIVAC I and early memories.