Patent ID: 6950509

Claim:
A method for determining a free connecting line in a switching center which has a number of subscriber access units which are controlled by a switching center, comprising: connecting the subscriber access units and at least one line trunk group in the switching center to one another via a switching network and/or internal lines, via which they can pass on calls between their connections; connecting at least one of the subscriber access units via a group of transmission lines, which includes a number of transmission lines, to in each case one other switching center; forming at least one logical group of lines with at least one of the group of transmission lines of a subscriber access unit and a group of lines which has a number of lines of the line trunk group, the at least one logical group of lines connecting the switching center to the other switching center; passing on a call via one of the lines in the group to the other switching center when an incoming or outgoing call, which is intended for another switching center, occurs in a switching unit; checking, when an incoming or outgoing call occurs at the subscriber access unit, to determine whether a connecting line which leads away from this subscriber access unit in the group of lines is free for a call to the desired switching center; and setting up a connection to the other switching center via this connecting line if one of these connecting lines is free.