Hello
I have Planet VIP-260 2 fxs
It's stable regiserd on 3CX server
make and receive calls viry nice on both fxs ports
but I can not transfer,park or hold calls
transfer and hold are features that our system does but your ata should support them also and have some special code to do this. For example on the SPA3102 its *98 by default (although its configurable) for blind transfer.
and flash on the phone is used for onhold usually.
Call park is not a feature that 3cx does if you mean call park in the sense that you put down the phone and pick it up from somewhere else
There is call pickup if one phone is ringing and you want to pick it up but no park feature.