IEEE 802.4

The Token Bus(IEEE 802.4/ ISO 8802.4) became known in connection with the Manufacturing Automation Protocol( MAP), but is of minor importance. It is a wideband system with AM/ PSK modulation.

This CATV-compatiblesystem uses a modulation scheme in which the carrier is changed in both amplitude and phase, allowing more information to be transmitted. Duobinary precoding with five amplitude levels makes it possible to realize a data rate of 10 Mbit/s on 6 MHz channels. Standard transmission rates are 1.544 Mbit/s on a 4- or a 6-MHz channel, 5 and 10 Mbit/s on a 6-MHz channel, and 10 or 20 Mbit/s on a 12-MHz channel.

The 802.4 working group is no longer active.