U.S. Patent No. 5183404, by Stephen C. Aldous and Guy M. Dake of Megahertz Corporation, a division of US Robotics (now 3Com).

XJACK is a invention that allows a direct connection between phone or ethernet cables and a Type II PCMCIA card--i.e. no dongle necessary. The XJACK connector is a thin piece of molded plastic that pops out of the side of the PCMCIA card, as if you took a vertical slice of an RJ-11 or RJ-45 port. The cable plugs in vertically and the XJACK connector has springy little wires that make the data connection and a U loop of wire underneath to keep the male RJ-11/45 connector from going in too far. When travelling, the XJACK pushes flush into the PCMCIA card, leaving nothing sticking out.

In my experience (I have a 3Com Megahertz 10/100 LAN PC Card), XJACK is really nifty except for one thing: because the male connector is plugged in vertically, the cable is bent 90 degrees right at the connector and is under constant strain. I have to buy a new ethernet cable every six months. The XJACK connector itself however, is qutie durable.