Jeffrey, As already pointed out, the maximum line speed you can achieve with two analog modems are 33600 bps. To get higher (downstream) speed you will need a digital modem on one side (connected via a digital line simulator or the ISDN network).
PBX extensions has often limited bandwidth which means that you might not get the full 33600 bps regardless of the quality of the modems. I've seen PBXs which limit modem communication to 9600 bps. If you modems are of good quality, you should definitely get a 33600 bps connection through the line similator (or the regular phone line). Try to set the similator to flat line and something like -25 dBm receive level. Instead of using ATZ, load the modem's factory default values from ROM using the AT&F command, it should work on these modems. Make sure your COM port speed is higher than 33600 e.g. 57600 or 115200 bps. I would recommend that you switch off the error correction feature during testing as otherwise you won't see minor receive errors caused by "normal" line impairments. A good modem should be able to handle receive levels down to -45 dBm. Hope this helps. Roger Magnuson Managing Director TGC Communication AB Industrivagen 5, 171 48 Solna SWEDEN TEL: +46 856250053 (direct) FAX: +46 856250055 mobile: +46 707770594 mailto:ro...@tgc.se internet: http://www.tgc.se -----Original Message----- From: treg-appro...@world.std.com [mailto:treg-appro...@world.std.com]On Behalf Of Dr. Jeffrey Race Sent: Thursday, November 21, 2002 12:23 PM To: Telecom Regulatory Group; POSSI Newsgroup; OS2 Users Group Subject: Need advice on testing modems I am trying to verify the maximum connect speed of two modems connected to each other by various media such as two phone company lines, two extensions off local PBX, and various line simulators. I am using IBM PC Card modems that come with TP600s (and in one case a Lucent Winmodem in a 600X). Using default config ATZ I can never connect higher than 31200 V42bis, as reported by the connection string reported onscreen in the terminal software. But I think I should be able to connect at V34 or V90 at higher throughput. How can I configure the modems to utilize their maximum capabilities (ATZ should do?), why am I getting these anomalous results, and is there any logging or diagnostic mechanisms at hand (either inbuilt in these modems, or in any tools I might use) to determine why connection speeds are low. I have various other modems such as external USR Sportster which I can bring to party if would help in diagnosis. I am basically trying to study line conditions but have to make sure the hardware is running at top speed before I can assess the constraining effect of line conditions. All comments welcomed Kind regards, Jeffrey Race, today in Bangkok Thailand Tel +66 2 291-2235 (res) +66 2 279-6162 (ofc) Tel +66 2 339-8025 (ISDN-res) 209-4201 (ofc) Fax +66 2 688-4540 (backup +66 2 271-4956) Tel +66 1 239-8197 (mobile -- 24 hours) Tel +66 1 829-4682 (mobile -- odd times) Avoid spinal damage from computer use! Read "Cripples by Thirty?" <www.camblab.com/nugget/nugget.htm>
