ISDN has for years provided the preferred method for sending high-quality audio using publicly-available connections. The data path is circuit-switched and not shared with others and the consistency – and delay – of end-to-end connectivity is assured. However, many providers of ISDN have increased prices and have already announced that the service will cease, forcing the inevitable move to IP audio.

Over recent years, using IP Audio Codecs and the Public Internet for data connectivity has shown itself to be extremely flexible and reliable, allowing live broadcast from pretty well anywhere there is an Internet connection. Coupled with careful management of streamed data over what is a packet-switched connection, stable, reliable low-delay audio is no longer in question. On the other hand, there is a very large installed base of ISDN mixer-codecs from various manufacturers where the audio mixing and cue capabilities are well-understood and liked but these are only able to connect to the studio using ISDN.