Abstract: An arrangement for according station and attendant feature transparency between independently operational PBXs of a PBX network. Each PBX includes a switch processor, station lines and tie-trunks extending to other PBXs. Each PBX also has a Direct Memory Data Controller (DMDC) for transmitting service or feature related data messages associated with tie-trunk calls to other PBXs over data links. On an interPBX call, the DMDC in a calling PBX transmits a data message to a DMDC in the called PBX over a direct link between the calling and called PBXs. In the event there is no direct link between the calling and called PBXs, the DMDC in the calling PBX transmits a message over a data link to a DMDC at a tandem PBX which, in turn, sends the message over a link to a DMDC in the called PBX.