The PHASER module runs the signal through a chain of all pass filters, which brings a very distinctive sound when the filter stages are modulated. Well known is this sound by many pieces of electronic music in the 70's and 80's; especially with the SOLINA as audio source you get this unique spacey sound known from these days. With a switch you can select 4 or 8 stages; more stages make the modulation more deep and intense.
These merchants probably sell this module. Huh?
Tangible Waves Phaser 8-Stage