Before the emergence of digital units, engineers used tapes to generate delays (often termed tape-echo). Not only is it interesting to see how these delays worked, but it can also be easier to understand the basics of delays using tapes rather than the less straight-forward digital adaptation. Famous units such as the Echoplex and the Roland RE-201 Space Echo were designed around the principles explained below. Despite many digital tape delay emulations, these vintage units have not yet vanished—many mixing engineers still use them today. Delays are also used to create effects such as chorusing and flanging, which are covered in the next chapter.