What used memory delay lines for storage?

Memory delay lines were used in early computer systems and digital devices for data storage, particularly in the 1950s and 1960s. These devices, such as magnetic and acoustic delay lines, stored information by progressively delaying signals through a medium, allowing the data to be read sequentially. They were primarily utilized in some early mainframe computers and telecommunications equipment before being replaced by more efficient storage technologies like magnetic core memory and semiconductor memory.