If ethernet networking is your goal, a PhoneNet card will not achieve it. For starters, the Farallon installer could not find a fast ethernet (10/100Base-T) card, which was a fairly positive indication. PhoneNet is a proprietary name of alternative hardware for serial communication with Apple's LocalTalk, which is also a hardware monicker, used to implement AppleTalk. Farallon's PhoneNet was just a cheaper (than Apple's) implementation of the cabling for serial-port communication. There were a few fast NuBus ethernet cards made, by Farallon and Asanté at least, but they are much less common than Thin-net (10Base-2), Thick (10Base-5), UTP (10Base-T) and combinations thereof. It is also conceivable that your card is a NuBus LocalTalk to ethernet bridge. I've never heard of one, but that doesn't prevent the device from existing.
But your reference to the DB-15 port on the same card is puzzling. It sounds as if it is an AUI port, an older standard port style for ethernet. It should have clasps instead of nuts to hold a cable's connector snug and secure. Does it? Farallon's cattle-dog number for the card might help us to diagnose it and help you. Is the other port an RJ-45 (wider than a telephone socket) or an RJ-11?
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But your reference to the DB-15 port on the same card is puzzling. It sounds as if it is an AUI port, an older standard port style for ethernet. It should have clasps instead of nuts to hold a cable's connector snug and secure. Does it? Farallon's cattle-dog number for the card might help us to diagnose it and help you. Is the other port an RJ-45 (wider than a telephone socket) or an RJ-11?
de