Delay Line Definition/Meaning:
An electronic device that produces a finite accurate time delay
between a signal imposed on its input and the appearance of the same signal at
its output. These devices may be used as short-term signal stores or to provide
accurate delays in signal -processing circuits. In an acoustic delay line
electrical signals are converted into a pattern of acoustic (sound) waves that
travel through a medium between a transmitter and receiver.
Although delay lines are now rarely used as storage devices, an acoustic
delay line memory was used in one of the first computers that had a stored
program (ED-SAC, 1949). Quartz crystals were used as transducers and the ultrasonic
pulses were passed along a tube of mercury about 5 feet (1.5 meters) in length.
The delay was approximately 1 millisecond but it enabled nearly 1000 pulses to
be stored. Later acoustic memories used magnetostrictive transducers and
nickel-iron wire, with the electrical signals converted into stress waves.