The Route Advance Delay feature allows the search for an available trunk to be interrupted for a set time. After this time has elapsed, a more expensive trunk is searched for. However, if a cheaper trunk (1) becomes available within this time, the time is stopped and the relevant trunk group is assigned. If the search for a B channel is interrupted and if the delay timer is greater than two seconds, this will be signalled to the user by a short tone. It is therefore possible for the user to search in a cheaper trunk.