http://www.jimdunlop.com/product/tap-tempo-switch
The MXR Tap Tempo switch features adjustable tip/ring configuration so you can control the delay time of a wide variety of delay pedal types. This pint-sized foot switch is ruggedly built for a lifetime on the road.
The Echoplex Delay from Dunlop recreates the vintage warmth and modulation of the original Echoplex EP-3 tape unit. In addition to basic controls over the number of repeats (Sustain), the level of effect compared to dry signal (Volume), and the time of the repeats (Delay), at the heart of the pedal is a carefully crafted, all- original AGE control that emulates the sound of aging tape and machine parts that varies the delay tone from pristine to dark and dirty.
Featured here is its tap tempo functionality which can provide delays from 40ms all the way up to 4 seconds of delay time when you hook up an M199 MXR Tap Tempo Switch.