sandersr@ecn-pc.UUCP (Robert C Sanders) (07/07/86)
In article <1207@mhuxo.UUCP> gjphw@mhuxo.UUCP (WYANT) writes: > > While considering the purchase of a 1200 baud modem, I began wondering >if there is some optimum data rate for modem operations over the U.S. >telephone lines. I have seen a few advertisements for 2400 baud modems, First; almost ALL of the 1200 baud manufacturers, esspecially the onces who first designed them, offer 2400 baud modems. There are many available. >and read mention of 9600 bps modems becoming available. Where does >the retransmission rate due to lost bits negate the higher data >transmission rate? Yes, there are 9600 baud modems out. Two major manufacturers are marketing them (net- help me with the names!). From the articles that I have read (PC World, BYTE, MAC World), the modems use a mathematical coding scheme to encode the data to acheive an equivilant 9600-baud thoughput. Then, they adjust themselves by testing the line and determining the optimum speed -- they will drop to lower rates (8400, 5600, 4800, etc) in a continuously variable manner to get the maximum speed realiably. Because of this constant variability and change, both ends have to use the type modem from the same manufacturer, unless of course you set the modems to use the industry standard speeds of 2400, 1200, or 300. These modems, if I remember right, are Hayes command set compatible, with extensions for their own capabilities. - bob -- ------------ Continuing Engineering Education Telecommunications Purdue University "Time is a mouse that requires constant feeding..." -- me ...!ihnp4!pur-ee!pc-ecn!sandersr