| ??? 12/27/07 10:23 Modified: 12/27/07 10:55 Read: times |
#148776 - Not Tough? but costly. Responding to: ???'s previous message |
Andy Neil said:
Erik Malund said:
The only circuit I know of that is made for very long distance comm via 'strings' is the modem. Exactly - see http://www.8052.com/forumchat/read.phtml?id=148737 In addition to the "line driver" of the original post (which just launches the signal onto the long wires), he will also need a suitable modulation scheme - which is precisely what a modem does. Remember that PSTN modems achieve speeds well over 9600bps on lines that may be several miles long and over a hundred years old! And these same wires are used by digital technologies like ISDN and ADSL... So, again, look at how the telephone system does it - forget the bits you don't need (ringing, an exchange, etc), and just look at the line drivers. In particular, look at "private wire" circuits... I look for solution like RS485 a Kind , if it is feasible?. PSTN modems requires -48VDC to operate they dont work on unconditioned lines?. And ADSL is out out my scope , it is carrier modulated over high frequency domain and needs ISP protocols to establish connections. You have pointed correctly regarding the line driver capablities , buy which . Best/ AP |
