Amir Sela wrote: > US is the key word here. Who says that modems that are destined for > other markets than the US get this restriction enforced on them ? As > far as I know Israel's and Europe's Communication regulations are not > limited by FCC regulations.
We'll that's an interesting question. The FCC limitations do not apply here, but the reason for them does. 56k just uses too strong a signal for the phone lines to handle properly. So while it's legal, BEZEQ will never do it. BEZEQ only guarentees 28k on a POTS line. This is to allow "line splitters" (two voice lines on on copper pair) used all over the country by BEZEQ and to make ISDN a viable option. After all, If we all got 56k or even 52k from our dial-up lines, why would we buy ISDN? Also note that the "56K" signaling only works on short copper lines connected to analog to digital line switching hardware, with only digital paths in between and the remote end being an ISDN PRI (T1) (Bezeq calls it a PRA). So you can't get anything better than 33k calling modem to modem. > Again, correct me if I'm wrong, but AFAIK the modem connection speed > at the initial handshake time is not necessarily the speed in which > they will communicate for the entire session. The speed might go > above 48k in the middle of the session... No, it often goes DOWN, but it never goes above ititial connect speed. And rarely does it go up again. > > > > 4. 48,000 bits per second is 4,800 BYTES per second (8 bits to > Hmm.. I think there's a bug in KCalc or something. when I do 48,000/8 > I seem to get 6000... > > > a byte + > > 2 bits for the START and STOP RS-232 serial bits) > Anyone wishes to confirm this ? That the control bits are counted > into the modem's so called "BPS" ? Nope, 9600 baud and above modems are synchronous. They send a constant bit stream which stays in sychronization at each end. This allows 8 bit characters. However there are some hidden "gotcha's": All data is broken into packets. 1. If you have error control on each packet is verified and an response is sent back saying it's ok, give me the next one. 2. Compression can speed up the line. Even compressed data often can be shrunk 5 to 10%, which is significant when you look at it in small chunks. Note that IP does some error detection, but no correction. TCP does error correction, sequence checking, etc. Using TCP/IP over a dial up line with error correction may be a bit redundant. In streaming applications, it's best just to drop bad or late packets, and not retransmit them. Geoff. -- Geoffrey S. Mendelson Bloomberg L.P., BFM (Israel) 2 hours ahead of London, 7 hours ahead of New York. Tel: 972-(0)3-754-1158 Fax 972-(0)3-754-1236 Email: [EMAIL PROTECTED] ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
