METHOD FOR MINIMIZING CALL SETUPS IN ISDN PBX SYSTEMS

A method for operating an ISDN PBX¢110! for connecting M BRI lines¢13-15! connected to a central office¢12! to N terminals¢21-28, 31-38, 41-48! connected to the PBX¢110! (N>M), such that any B channel of any of the BRI lines¢13-15! can be connected to any terminal utilizing a connect in accordance with Bellcore National Standard N1-2. Each of the terminals ¢21-28, 31-38, 41-48! is associated with one, and only one, of the BRI lines ¢13-15!. The present invention achieves its advantages over the prior art by defining a plurality of EKTS groups¢1-4!. Each of the EKTS groups¢1-4! includes at least one of the terminals¢21-28, 31-38, 41-48! associated with each of the BRI lines¢13-15!. When an incoming call is received for a terminal associated with a BRI line that is currently busy, the call is connected by emulating a connection to a second terminal that is assigned to free BRI line and which is also assigned to the EKTS group to which the first terminal is assigned. In the preferred embodiment of the present invention, the number of EKTS groups¢1-4! is the smallest integer that is greater than, or equal to, N/(2M).