Two 990 s

Only if you like complete disasters.  Only one base, any number of CAB2's.

I was curious about this subject also..

Paul,

So, any number of cab2 remote units with one base…???

Yep, that is the way the system is designed.  Each CAB2 can control different or the same engine.

So I can sync two remotes to one base I have two systems can I just put them on different channels 

The remotes have to be on the same Legacy channel.

all remotes will talk to one base if on the same channel

at the club we run 4 and sometimes as many as 6 remotes at once. two trains on each line so we could run 8 remotes.

you get the idea.

But do they have to be the same software 

Raiderofcoffins posted:

But do they have to be the same software 

yes, the same version as the base communicate with the base properly.

Raiderofcoffins posted:

But do they have to be the same software 

no the system is backwards compatible.

You just want a single base on the layout. The number of remotes that can talk to that base is somewhere well above what you're going to use. The software version *should* be the same between the base and all the remotes  but it will work if its not, some features may not be available or not function depending on the version differences. 

Also, all the locomotive and layout information is stored in the base, not the remotes, so you can take your remote with you to other layouts and it'll have those locomotives already.

Can I use the other base as a charger or would it sync to that base by doing that

Since there is no way to turn it's radio off, the Cab-2s will try to talk to it, so I wouldn't even power it on.  this is why Lionel has the 993 set, gives you a 2nd handheld with only a charging base.  I have a 990 and 993, and the 993 charging base has never been out of the box.  The 990 base is more than enough to keep two remotes charged.  The remote should only be in the charger when it needs charging.  As long as you rotate the remotes, you'll never need to charge more than one.  Storing the remote in the charging base is bad for the batteries and will shorten their life.