On Mar 8, 2011, at 2:34 PM, Scott Newell wrote: > At 01:22 PM 3/8/2011, Dan Shoop wrote: > >> And, just to pick nits, it's 19200bps, not 19200 baud. The baud rate >> is how fast you're signaling, not the gross bit rate. You're >> probably still signaling at 9600 baud yet transmitting data at 19200bps. ;) > > I'm confused. Is there some channel coding going on over that > non-modem serial link that would give you more bits per symbol?
You're probably confused with the second sentence which I didn't intend to relate specifically to the first in this specific case. No assignment of encoding or symbol set was given for what we're discussing over the circuit. What we're discussing is therefore only the bit rate. The symbol rate is related to, but should never be confused with, the gross bitrate. It's only correct that the baud rate is the bit rate if the bit rate /is/ actually the baud rate. (That may sounds tautological, but it's not.) While true in this circumstance because it its the interace speed between the DCE and DTE it may not be in all cases which is why the correct terminology to use here is bps here since it's what the DTE cares about and what the DCE is sending, no further baudot is at play between the DTE/DCE pair, only possibly between DCEs that may, or may not (even in this case) be in between. When discussing baudot rates each signal symbol can represent or convey one or several bits of data. And even with ASCII there are still seldom used shift codes and escape codes which can effect bit to signal rating. So in any event the correct unit for expression here in this case is bps, and not baud. They do relate, but should not be confused, and since the baud and bps rates can be quite different bps is what should be stated. But yes, in this case it's very most likely still one channel on the null modem serial circuit. In this case they are in all likelihood the same but the correct rating for expression would still be bps. Often though you commonly can end up with fewer symbols per second in such circuits, while in modem circuits you often see more bits per signal event. Data may be represented by the transitions between symbols or even by a sequence of many symbols. Simple examples in differences: all "zero" symbols aren't marking; a symbol may have more than two states so it may represent more than one bit. Sorry it's a pet peeve of mine since the days of explaining the difference between the bps an baud rates as seen between different teletype models since different models used different baudot codes. -d ------------------------------------------------------------------------ Dan Shoop Computer Scientist U.S. Technical Services [email protected] GoogleVoice ............... 1-646-402-5293 * Nextel .................... 1-714-363-1174 Operations TOC (24/7) ..... 1-866-901-USTS USTS Offices .............. 1-714-374-6300 For immediate response or urgent matters please speak to the Duty Officer at the USTS Tactical Operations Center (above) _______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
