This is probably going to seem like a silly thing to ask, but I have an Ethernet 10BaseT Micro-ceiver that I am using to convert UTP to AUI for an AB 5/40E.  On this Micro-ceiver, there is a switch labeled SQE.  The installation instructions indicate that this switch should be on when connecting to a DTE or workstation and off when connecting to the AUI port of an Ethernet repeater.  My question is this: What does SQE stand for?

Quote

Signal Quality Error (SQE) The SQE test or 'heartbeat' is a test signal generated on the cable after every transmission to assess the ability of the transceiver to detect collisions. The test is a very short frame that is too short to look like a collision. Ethernet 1.0 did not have this in its standard and 802.3 says that repeaters must not connect to a transceiver that generates the SQE test because of the Jam signal that is designed to prevent redundant collisions from occurring. The option is normally available to turn off SQE test for this reason.

Turn it off.  Nobody uses it anymore.

Agreed.  

I have a handful of various AUI/10BaseT and /10Base2 transcievers that I use with the PLC-5E controllers and sidecars in my demo inventory.

All of them have the SQE switch off (or in the case of the ones with jumpers, stolen for another application!)