Cisco Presentation Guide

Signal Quality Error (SQE)
signal of AUI transceivers
• sent by a transceiver back to the controller to let
the controller know whether the collision
circuitry is functional.
• designed to fix the problem in earlier versions of
Ethernet where a host does not know if a
transceiver is connected.
• SQE is active:
• Within 4 to 8 microseconds after a normal transmission
to indicate that the outbound frame was successfully
transmitted
• Whenever there is a collision on the medium
• Whenever there is an improper signal on the medium
(jabber, cable short)
• Whenever a transmission has been interrupted
© 2005 Petr Grygarek, Advanced Computer Networks Technologies
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