An internal data channel is a connection between the system's telephony and LAN interfaces. For example a Voicemail connection, an internet connection or a RAS user.
Calls using a VCM channel (for example VoIP calls and Avaya 4600 and 5600 Series phones) do not use a data channel.
The number of data channels in use does not necessarily match the number of users:
The maximum number of data channels that can be simultaneously in use for voicemail is restricted. These channels also require entry of an appropriate license.