Hey Barclay...excellent question, you'd think there would be just such an adapter..there are all kinds of adapters for computers....unfortunately........in a single device there is no way to convert these two technologies*.
..ok..i'll try to answer without making anyone's eyes bleed and/or without writing a book.
1) the first problem is the media itself. DSL connections work over POTS (plain old telephone system),,and cable, well is cable.....
2) DSL uses a frequency barrier to determine if it is data traffic...voice calls occur in the 0-4000Hz range, data transmissions are >4000Hz. (didn't you ever wonder what that DSL line filter was doing? It filters out signals above 4000Hz so only voice traffic goes to the other telephone equipment you have connected in your house) At the Telco the connection goes into what is referred to as a DSLAM (DSL access multiplexor). At the Telco's end this is what splits the signals based on the frequency. 0-4000Hz goes to the voice switch. (listens for DTMF tones, creates circuit..PCM encoding..blah,blah..) above 4000Hz goes to a Carrier Router owned by an external ISP or internal servers that provide content, web access..all kinds of goodies)
3) Cable uses different media and different encoding schemes. It goes as far as using different encoding schemes for upstram and downstram data. The basis for that encoding is MCNS (Multimedia Cable Network Systems) MAC. Yes, you guessed it..data flows in cable land are based in part on MAC addresses.
Due to these imcompatabilities..you cannot convert one to the other...
HOWEVER, depending on the model of broadband router you have it may be able to connect cable OR xDSL, just not both....the documentation or vendor's web site should provide you with this information. From the modem (DSL or CABLE), you are just connecting to the router with a cat5 or cat6 ethernet cable.
*Notice in the begining, i said "in a single device"....VERY, VERY large routers...CISCO'S CARRIER series..(no! you don't have enough money for one of these...lol)....have add-on connection cards that can accept connections from ATM, ADSL, HDSL, SDSL, CABLE, FRAME RELAY, SONET...etc. and route/switch them onto very large networks.....(but that is a story for another nite.....lol)
Edited by brianmil0923, 16 September 2005 - 10:44 PM.