"You couldn't get those beautiful shades, those tremendous tonal things, with just a Fender Twin." - Andy Summers, 1991
In the mid-1980's, Andy Summers changed his effects setup from a pedal-based system to a Bradshaw-style rack system. The Bradshaw rack is basically a coin phrase for any kind of rack system which includes multiple effects processors and a switching system at the player's feet (invented by Bob Bradshaw.)
Andy's most used rack effects during this period were his Lexicon PCM-70 and Eventide Ultra Harmonizer (H3000-D/SE).


Lexicon PCM-70 (top) and Eventide Ultra Harmonizer
The Eventide was particularly heavily featured during Andy's live performances. From Guitar Player, April 1991: "I use alot of the Eventide onstage. I don't like to drench everything in echo. I like to create this great cathedral of sound at some moments and at other moments use a bit of fuzz and blow."
From the same issue, on explaining how his effects rack had become a composistional tool like the guitar synth was to him in the Police days: "I do an echo loop introduction to 'Earthly Pleasures' from 'The Golden Wire' with me playing inside the loop in an Indian mode. There's a great moment in the show where I do a transition from a piece called 'Vigango' - a float area where I do this echo trip with Indian raga playing. The band comes in underneath with a slow hypnotic groove. Very effective and very psychedelic."
Not much is known about what pedals Andy used during this era - possibly hundreds in his quest for tone. However, one is known for certain:
Andy used a ProCo Rat distortion pedal during these years quite frequently. Many guitarists favor this pedal, though
it is most preferred by metal players. This is probably because this pedal was designed with a circuit that reduced
overall frequency response, allowing anyone to play high, hard-to-catch harmonics at will. This pedal is effective
when used with very harmonically rich or overtone-laden guitars equipped with tremolos... like Andy's Steve Klein
Electric.
By Greg Danielak - 2001