1.
If you ~ with someone, you join them for a particular purpose.
They linked up with a series of local anti-nuclear and anti-apartheid groups...
The Russian and American armies linked up for the first time on the banks of the river Elbe.
= join up
PHRASAL VERB: V P with n, pl-n V P
2.
If one thing is linked up to another, the two things are connected to each other.
The television screens of the next century will be linked up to an emerging world telecommunications grid.
= connect
PHRASAL VERB: usu passive, be V-ed P to n, also be V-ed P