What is the limit of the Farscape Communication device

the wiki says:

"Comms or communication devices were integrated systems connected to and controlled by Leviathans such as Moya.

The devices had a fairly wide range, but a distinct limit. Portable units could be attached to clothing and used to communicate with other portable devices in addition to the Leviathan and her Pilot."

-- but it doesn't say what the limit is or have any references to their justification of that. I was sure that they were FTL communication but can't recall why.