The innovaphone PBX enables the set-up of several waiting queues. Registration is not necessary and, therefore, there is no need for a port license. The number of waiting calls in a waiting queue can be limited and a timeout feature releases callers that have not been retrieved from the waiting queue. A selection of DTMF tones is tailored to the announcement so that the waiting caller is redirected to the correct contact. This enables ACD to be used efficiently, already in the waiting queue.