Two B Channel Transfer or TBCT for short, is an emerging telephony technology, where a telephone conversation on an incoming and outgoing line on a PBX can be passed "up the chain" to the telephone company, freeing up two lines on the PBX. TBCT permits more efficient routing and use of available telephone lines, because callers can “pair” together, without loading the PBX with the call for its entire duration. This makes telephone call routing much more scalable.