Delta O2 "Touch" kitchen faucet question

[fatfenders]

6 years old. Never a problem until it sprung a leak recently. Took the solenoid apart, cleaned things up, put it back together and no more leak.
So that is not the issue. In fact, there is nothing wrong with it now but I would really like to understand how the darn 'touch' 'off' toggle works. It has me stumped. Referencing the images below... (3) shows how the water enters (4) shows how the white and black parts mate and the diaphram that, when pressurized stops the flow, and (5) shows the cylinder that houses the black and white parts. (1) and (4) show the bottom and top of the black part respectively. (2) shows the small rubber tipped piston and (5) shows where the piston goes. When the solenoid is energized it pushes the piston up and gently (there is a spring between the solenoid plunger and the piston) up against the small port shown in (5).
Somehow when the port shown in (1) is sealed off it causes the diaphragm (on the other side) to press against the base of the white part and stop the flow(I think). Also, I have no idea what part the larger opening just below the small port (1) plays.
If anyone has any thoughts on this (good, bad, indifferent) I would love to hear them.