A wide selection of Ethernet cards offers more than one connector, the boards can be used via a BNC-connector for Thin Ethernet (10base2) or via an RJ-45 connector for Twisted Pair Ethernet (10baseT/UTP) (some boards even offer a connector for the 'original' Thick-Ethernet (10base5), which is now only used in large networks to create Long-distance backbones.

First: although the card has 2 (or more) connectors, it has only ONE set of electronics, so ONLY ONE connector can be used (it is NOT possible to connect BOTH a BNC/Coax cable and a RJ45/TP-cable and to communicate over both connected network cables).

The question is now: is the board 'smart' enough to work it out itself, in which of the plugs you connected your cable ?
If the board needs to be configured, but is NOT configured for the plug, where you have connected the network cable, there will be no communication !

There are quite a number of boards, where this is NOT configured automatically, but you as the user have to define it.

1) Jumpers: some boards still used jumpers to define port-address and IRQ, and a few of them have also a jumper defining, on which connector to use (some of the popular NE2000 compatible boards have such jumpers).

Search for something like above, and set the jumper properly.

2) Softset-boards: Some boards have no jumpers, but require to be configured via a special software configuration utility. If you have such a "Soft-Set" configurable board, have a look to see, if one of configuration parameters define the connector to be used (I think, the 'original' INTEL EtherExpress requires this type of configuration)
Example: 3COM Etherlink III 3C509B:
using the setup/diagnostic program 3C5X9CFG.EXE:


look for "Transceiver Type": on new boards, the factory default should be "Auto Select" (so the board will detect itself the type of connected network).
But when you get used boards, it may have been pre-configured:

Put is then back to "Auto-Select" or define your type of network cable.


3) Win95 adapter properties: Some boards (like the on-board AMD-network adapter on some older HP-models) are configured via the "properties" of the "Network adapter", accessible from the "Network applet" in the "Control-panel".
Example of an Intel Ether-Express: "Transceiver Type:"


Example: 3COM Etherlink III PCMCIA 3C589:

Windows95:

Windows NT4: