ISDN-based system for making a video call.

The present invention relates to a call with sufficient quality for simple medium telephone or conversation level (audio) service, inclined by an ISDN video telephone and directed to another ISDN video telephone, which is converted into a multi-media ISDN call. (audio and video) by a) maintaining the connection for the conversation level call, while the ISDN audio and video connection is established on a different ISDN subscriber loop bearer channel than the bearer channel that is used by the conversation level connection, b) switch the audio signals of the conversation level call to the ISDN audio and video connection, once the ISDN audio and video connection is established and c) fragmented from the initial conversation level call.