fff@eng.microplex.com (Fred Fierling) (02/05/91)
Have you ever noticed that Western Digital Ethernet adapters have what appears to be a capacitor that is partially sawed through? It's near the thick ethernet connector. It might even be a varistor. I've seen it on older WD8013 EBT's and on their latest (Rev B). Does anyone have a clue why they do this? -- Fred Fierling fff@microplex.com Tel: 604 875-1461 Fax: 604 875-9029 Microplex Systems Ltd 265 East 1st Avenue Vancouver, BC V5T 1A7, Canada
BILLW@MATHOM.CISCO.COM (William Chops Westfield) (02/05/91)
Have you ever noticed that Western Digital Ethernet adapters have what
appears to be a capacitor that is partially sawed through? It's near
the thick ethernet connector. It might even be a varistor. I've seen
it on older WD8013 EBT's and on their latest (Rev B).
Does anyone have a clue why they do this?
Hee hee. I am pretty sure that this is a spark gap. Most ethernet
transceivers have them, even the external boxes. Since the WD boards
have an internal transceiver, they also have their own spark gap.
Spark gaps have interesting electrical properties. In theory, a high
enough voltage on the cable will cause a nice spark their, before the
inductance of, say, the PC board traces, lets the voltage through to the
more sensitive components further inside your computer.
As a software sort of guy, devices with spark-gaps make me nervous.
T1 CSU/DSUs have several, like one on each incoming wire.
BBZZZZZZZZZ ZAP!
BillW
-------alan@curly.Viewlogic.COM (Alan Medsker) (02/09/91)
They're trimming the capacitance of the device to be exactly what they want. 3Com does it, too, and probably others. A lot cheaper than a trimmer cap. Alan -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Alan Medsker Viewlogic Systems, Inc. Voice: (508) 480-0881 293 Boston Post Road West Fax: (508) 480-0882 Marlboro, MA 01752 Internet: amedsker@Viewlogic.COM cc:Mail: Alan Medsker at Viewlogic CI$: 76376,662 BIX: amedsker 2 Meters: WB0SQR =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= My opinions, of course. And don't hold me to them. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=