Delay is a time-based effect that copies your incoming signal and plays it back one or multiple times after a period of time. That period of time (Time) and the number of times it’s played back (Repeats) depends on the delay itself.
In the early days of delay effects, your guitar signal was recorded on a magnetic tape within the unit and then played back shortly after. Ubiquitous analog units, like the Echoplex and the Roland Space Echo, employed this technology.
The Binson Echorec replaced magnetic tape with a magnetic disk that functioned a lot like your computer’s hard drive. But both of these styles of analog delay meant that the units themselves were large, cumbersome, and hard to maintain.
The 1970s saw the invention of “bucket brigade” devices—the first all-electronic pedals that could be used to produce time-based effects—which were much smaller and easier to use on stage than previous analog options. A sterling example of the era would be the Electro-Harmonix Deluxe Memory Man.
From the late ‘70s on, technology continued to advance, leading to more functionality being packed into smaller packages. Today, you can pick up a digital delay that boasts a huge menu of delay types and extra functionality—analog, tape echo, reverse delay, looping, tap tempo, modulated delay, and more—in one small chassis as easily as you can pick up an analog unit.