glen@aecom.yu.edu (Glen M. Marianko) (12/08/89)
I've been trying to track down the difference in the AUI cable design
between AUI cables for use with 802.3 equipment vs. Ethernet I and II
equipment. One spec I saw shows the shield/drain wire connected to
pin 4 for 802.3 yet all the 802.3 AUIs I saw have it on pin 1.
Also, according to ISO 8802-3 and ANSI/IEEE 802.3 bible, shield
is on pin 1 yet each sheath of shielding for each pair is also
supposed to appear separately on the AUI connector. Nobody ever
does this in practice. Instead all the TP sheilds are twisted
together with the drain wire in the middle thus shorting all the
shields to the drain. Is this ok?
--
-- Glen M. Marianko Manager, LAN Services Glasgal Communications, Inc.
151 Veterans Drive Northvale, New Jersey 07647 201-768-8082
glen@aecom.yu.edu - {uunet}!aecom!glen (Courtesy of AECOM & unaffiliated)pat@hprnd.HP.COM (Pat Thaler) (12/12/89)
According to 7.4.3 of ISO 8802-3 (IEEE 802.3) ".... Individual shields for each signal pair are electrically isolated from the outer shield but not necessarily from each other. The overall shield shall be returned to the MAU and DTE Units via the AUI connector shell as defined in 7.6.2 and 7.6.3. If a common drain wire is used for all the signal pair shields, then it shall be connected to pin 4. Individual drain wire returns for each signal pair may be used (see 7.6.3). It is recommended that individual drain wires be used on all control and data circuit shields to meet satisfactory crosstalk levels. If individual drain wires are used, they shall be interconnected within the AUI cable at each end and shall be connected at least to pin 4 at each end of the cable." So the requirements are for: Overall shield to connector shell (which must be conductive) Drain wire(s) of individual shields to pin 4. Individual shields isolated from overall shield. The individual shields may also connect to the other shield pins. Ethernet did not require isolation between the individual shields and the overall shield. It did not require that the connector shell be conductive. All shields were connected to pin 1 as well as the shell. Pat Thaler