Limit communication speed rang

I'm not sure I am properly understanding your question, but I assume that
you are asking if there is a way to make an Ethernet (10 Base-T or 100
Base-TX) device work at longer distances than the normal 100 meter cable
segment limitation.

First, this really isn't the appropriate forum for such a question, and you
would be much better off asking it in comp.dcom.lans.ethernet instead.
However, I have run across this before, and a quick answer is possible.

You can't change a NIC card's speed except that you can select 10 Mb/s or
100 Mb/s operation in many cards. You cannot select other speeds, as they
are not part of the 10 Base-T or 100 Base-TX standard, and 1 Base-5 died
many years ago. DSL service is connected to the LAN via either a router or
a DSL modem, which is a bridge. Either device performs a speed conversion
as it forwards messages between the LAN and the DSL line.

Another alternative you can use is an Ethernet extender that converts to a
DSL-type signal and then back again on the other side, if you own the copper
cabling between the two sides and your distance is somewhat limited (say
18,000 ft. maximum). You can find these at Tut Systems (#)