GarrettCom MAGNUM H80B - Manual (Page 27)

Magnum H80B and H80P Personal Hubs User Guide (07/95)
GARRETT
23
Preamble Regeneration: Personal Hubs add bits to the preamble so
that the output packet contains a minimum 64-bit preamble per the
Ethernet standard.
Collisions: When carrier is detected simultaneously on multiple
ports, a jam pattern is generated on each port to create a collision
condition. When a collision signal from one port is detected, it
generates a jam pattern to other ports.
Fragment Extension: Personal Hubs will automatically add bits to a
received data packet of less than 96 bits (a "fragment") so that the
forwarded packet is 96 bits long.