This page is helpful with how 120 channel system works (it's from MedEL site but the concept is what 120 System does)
http://www.medel.com/ENG/INT/30_Advanced_topics/999_finehear.asp
"Field Shaping... Current steering, one way of implementing field shaping, can provide additional fine frequency information by controlling the precise location of stimulation between two electrode contacts. As a result, a pitch between those two frequencies can be created, allowing for more distinct and predictable pitch percepts."
That's how CII creates 120 channels.
http://www.medel.com/ENG/INT/30_Advanced_topics/999_fs.asp
It gives a visual representation of what envelope and fine structure mean in terms of hearing.
http://www.medel.com/ENG/INT/30_Advanced_topics/999_finehear.asp
"Field Shaping... Current steering, one way of implementing field shaping, can provide additional fine frequency information by controlling the precise location of stimulation between two electrode contacts. As a result, a pitch between those two frequencies can be created, allowing for more distinct and predictable pitch percepts."
That's how CII creates 120 channels.
http://www.medel.com/ENG/INT/30_Advanced_topics/999_fs.asp
It gives a visual representation of what envelope and fine structure mean in terms of hearing.