What is ISDN?
H-Channel
The H-channel is used for high-speed user data traffic at bit rates higher than 64Kbps. Examples of services which require these higher rates are fast facsimile, teleconferencing, and video. An H-channel user can subdivide the channel using TDM to meet specific requirements.
DIVA T/A ISDN Modem Reference Guide ◆ Page 7