ISDN has 3 channels: B-channel, D-channel, and H-channel. The B-channel is responsible for a speed of about 64 Kbps, usable for home utility. The D-channels are responsible for speed within 16-60 Kbps, used for the B-channel signaling, while the H-channel provides speeds ranging from 384 Kbps to 1920 Kbps.