Well........not sure. Mine (which has failed totally and is in the shop!!!) has 3 canisters next to the reservoir. Two are for right/left hydraulic jacks. The 3rd one is for the slides. However, there is a separate 4th smaller canister connected via line to the top of the reservoir......and that is (I've been told) the device (it has a name, it escapes me) that says "Close bedroom slide first, close dining room next, then kitchen". It's not some program, it's mechanical.......
And that's all I know about it, and is subject to being way off base!
I just know mine ain't workin' at the moment!
"Next to prayer, fishing is the most personal relationship of man" Herbert Hoover
"American by Birth, Southern by the Grace of God"Lewis Grizzard
2016 GMC Denali 3500Dually--2017 CC 36CKTS