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WTC Modem Questions Tips That Apply to PC Systems and High Speed Modems

If you are not getting the connect speeds or the modem is dropping out the problem is usally one of the problems outlined below, sometimes it is a easy problem to fix. Sometimes the problem is a hardware problem that can not be fixed with your current hardware.

MODEMS
Sometimes people think they have a high speed modem when in fact they do not, modems are sold as data modems, data/FAX modems and data/FAX/Voice modems. The modem may be a 2400/9600 modem that means it is 2400 Data and 9600 FAX. Read your modem manual and determine if the modem is really a High speed modem. If you do not have a manual for your modem check the UART if it is a internal modem(See UART'S). If the modem can only connect at 2400 then your modem may be a 2400/9600 data/FAX modem and 2400 is the highest data speed you can reach.

COM PORTS
Avoid IRQ conflicts you can't use both COM1 and COM3, or COM2 and COM4, at the same time because they share an interrupt. This can cause the modem to drop the line. Try disabling COM3 and/or COM4 and move the modem to COM2. If the mouse is on COM1 and the modem on COM3 then they are sharing the same IRQ just moving the mouse at the same time the modem is using the IRQ can cause the modem to drop the line.
Some internal modems allow you to pick the IRQ to use with your Com Port, while this may work some software packages expect to "see" the Com Port on the default IRQ. Other IRQ conflicts may cause the software to drop the modem so check all your IRQ's.

COM2 has a higher interrupt priority than COM1 if possible use COM2 if you have a marginal system or you are running lots of tasks. Run MSD.EXE, the Microsoft diagnostic program which comes with current releases of both DOS and Windows (EXIT Windows before running.)to see any COM Port IRQ conflicts.

UART'S For External Modems
This section applies more External Modems most internal modems come with a custom UART on the modem, you can use this information to check the UART in a Internal modem.
Run MSD.EXE, the Microsoft diagnostic program which comes with current releases of both DOS and Windows (EXIT Windows before running.) to see if you have a 16550 UART
If the UART is not a 16550 you will need to look at replacing the UART if it is a internal modem then it may be a low speed modem (2400) check your manual for the DATA speed. If the UART is a 8250 or a 16450 it will cause problems in CRC errors, com overruns with a high speed modem.

RPI Modems
RPI modems are inexpensive modems which use a special Rockwell chip set that (in most cases) implements error correction and data compression in software instead of hardware.
While the concept of using your PC's CPU to perform compression and error control is reasonable RPI has earned the bad reputation it has due to past limited software support, performance problems, and deceptive packaging which gave little clue to purchasers that the modem they were buying was missing hardware error correction and data compression. Most people do not advise using for those reasons,if you own a RPI make sure that your system can handle the modem and get the newest drivers for your RPI modem A RPI modem can be sold under any brand name if you are looking for a new modem price out a modem with error correction and data compression in hardware.
There are 14400 and 28800 RPI modems if are having problems with your modem check and see if it is a RPI modem.

Connect Speeds
Here is quote from a paper by "Of Line noise, The Phone Company, and Your Modem" by Patrick Moore, Supra Corp This explains why you may not be getting 28800 connects or throughput

 -  Repeatable results with V.FC/V.34 modems on real-world phone 
     lines are sometimes difficult to obtain.  Unlike V32.bis modems, 
     V.FC/V.34 modems will actually modify their data coding (symbol 
     rate) and transmit levels during the connect phase.  Very minor 
     differences in the phone line can lead to quite different results.

  -  A 28.8K connection on some real-world lines may not occur very 
     often, if it occurs at all.  Preliminary testing in the lab 
     indicates that "normal" phone line attenuation makes a 28.8K 
     connection difficult even in the absence of line noise.  This is 
     not surprising considering that the V.FC & V.34 coding schemes are 
     relying on the bandwidth of the phone system being greater than 
     what is actually available in some areas.  Very high-speed 
     connections assume that there is a substantial amount of digital 
     technology in the system (thereby normally increasing the usable 
     bandwidth).  Some users are going to find that their local phone 
     system effectively limits them to 16.8K or 19.2K.

  -  Both the originating and the answering modem are adjusting to 
     their line conditions during the connect phase.  The fact that 
     a connection to a given modem at a given location occurs at a 
     lower rate (19.2k for example) may have nothing to do with the 
     modem the call is placed with, or the location it is placed from, 
     as the modem on the other end may be adjusting the baud rate down.



For the above reasons, many people will never see 28.8 or even 26.6 CONNECTS with their 28.8 modem. The easiest way to find out if its your phone line or your modem is to find someone who usually gets 26.6 or 28.8 connects, and try your modem on her system, or his modem on your system. You will most likely find that the problem at your end is phone-line related.

Wiring
The telco wiring may causing poor connects, or a bad or loose wall plug connection. The only way to indentify this problem is to run a new line to the modem directly from the Telco Block and make sure everything else on the block is disconnected. Where visible, inspect the routing of the phone wiring to assure it steers clear of other wiring and electrical devices placing the telephone wire beside other wiring may cause "line noise" in the phone line, check ALL the telephone wiring the noise may be caused by a line other than the line to the modem. One solution is use a teleprotector, run a a new, dedicated line from the telco block to the modem jack. Put a teleprotector on the modem line so when the line is in use the rest of the telco system is locked out. I have seen teleprotectors sold in most large stores in the telephone department cost I have seen is 6.00 - 12.00 dollars. Also try replacing the wire from the Modem to the Wall jack I have seen modems that will work with one wire but not one that looks the same, and both work with a handset.Sometimes the modem or the wall plaug may not be connecting quite right replacing the wire from the modem to the wall plug will sometimes solve the problem. Adding a teleprotector is a really good idea even if you are not having problems a teleprootector will lock out the other lines so if some one picks up a phone else where in the building it will not be active. Unless you have a data line the telephone company only has to supply with "voice grade" line if your lines are really bad for data, the telephone company may not do anything for you but if you complain about FAX problems they may fix the problem.

Telephone Services
If you have extra telephone services like Call Waiting make sure the service is turned OFF when you dial out using the modem. If you do not turn the service off the may drop the line or lose all the data. Some services like call waiting you can turn off in the modem INIT string if have a extra telephone service look in the Phone Book to see how to turn the service off.

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