Modem Help

Conditions and factors that affect analog modem (dialup) connection and speed


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This page includes some tips that apply to all analog modems and two scripts to try for the Macintosh internal modem.
(While some may prove useful to others much applies to the U.S. and likely Canada.)
Things to check or change:
  1. The phone company only gives you a usable voice grade connection.  Check that you have this by dialing a single digit (other than 0) and listen carefully.  Any noise, hum, or hearing a conversation should prompt a service call after making sure that it is not caused by your equipment or in house wiring.
  2. The phone company often leaves extra wiring connected to make it easier for them to reuse your line for a different house.  Ask them to remove any bridging clips.  This is the major part of conditioning a line for DSL.  Try to convince the guy that comes to check out the noise on your line!
  3. Most in house wiring (the part you are now responsible for) is the old so-called Category 1 (no markings 4 wires) which easily picks up noise and is subject to crosstalk between the two lines (if you have two).  Consider replacing it with Cat. 3 or higher (Cat. 5e recommend).
  4. Call waiting will usually cause a modem connection to drop.  Disable it by adding the disable sequence (usually *70) and a comma in front of your ISP's modem phone number.
  5. Anyone picking an extension can cause a modem connection to drop.
  6. Some services like voice mail modify the dialtone at the beginning of the call.  Have the modem not wait for the dialtone (it will wait 2 seconds and then dial blindly).
  7. The use of anything other than the original cord or a high quality Cat. 5e cord to connect the modem to the wall jack may cause problems.  This is especially true of small wind-up cords.  DO NOT use long or extension cords.
  8. Certain types of phone line surge suppressors (those that use MOVs) are not suited for high speed use.  Try without when no storms are in the area.
  9. Try without any other equipment connected to the phone line.  Phones, fax, other modems, or whatever.
  10. V.90 and V.92 high speed connections use similar techniques to ISDN and are subject to the same limits.  18,000ft on 24 guage or larger wire, no repeaters, no loading coils.  Basically if the V.90 or V.92 is not stable use V.34.
  11. In the US by law connection may not go higher the 53,333bps (limited at the ISP).  I have never gotten better than 49,333bps on a real phone line (~10,000ft from CO) with anything other than a US Robotics modem (which has a serious flaw the "spiral of death").
  12. The further you are from the CO (Central Office - really the switching office) the lower your connect speed.
  13. Compression should always be enabled on hardware modems and likely on software modems as well.  This allows text and some other files to transfer at 2.4 times (V.90) to 3 times (V.92) the connect speed.  Things that do not speed up: images (.jpg .gif), secure web pages (https://), other already compressed files (.zip .hqx and Mac .bin)
  14. Error correction should allways be turned on.  Because the modem handles errors on much smaller blocks of data the retransmit time is less and the chance for another error is also less.  If it were not on the error will be caught at some other layer, though some types of transmissions are deliberately lossy.
  15. Check the modem manufactuer's support site, normally you want the next to last upgrade unless the last one addresses the problem you are having.  All software like wine or cheese should age a bit.  (Give people time to find and document bugs in the latest release!). 
  16. Run a speed test both when first connected and after being online a while to see general performance.
  17. Other than during testing always use a modem surge suppressor rated for 56k modems (test speed with and without).  What the phone company uses on your side will only protect old style phones.  What might be built into the modem only protects from a surge between the two phone wires.  A lightning induced surge will find the best way to ground, usually this being though your computer.  Nothing protects from a direct hit, backup frequently!
  18. You might experiment with building this noise filter presented by Randy B. Singer (co-author of The Macintosh Bible).  He also has other useful OSX 10.2.x tips as well as law office use of the Mac.
  19. Check Macintouch and their Apple modem problems special report.
  20. Some older lighted (incandesant white) dial phones (such as TrimLine) had power for the light supplied by a transformer (7VAC) wired to the second line (black/yellow) wiring.  Unplug the transformer until separate wiring can be run.  Run new Cat. 5e for the phone and use the old wiring for the light (be sure none of the old wiring remains connected to the phone wiring other than at the jack by the phone).  Newer ones run from phone line power, and likely are not a white light (though a blue-white is possible).
  21. [added Sept 25 2003] AOL invalidates any speed test using an image with a color depth greater that 256 colors since it converts all images to this limited range of colors.  (will try to find a test site that addresses this shortcoming)
(There is at least one report these help with MacOSX 10.2.4, I have not yet tried to confirm this.) These are modem (CCL) scripts for the Apple 56K internal modem.
They should be tried by anyone with this model of modem.

Some newer models are on internal USB ports (will list if I can find a definative list).  These scripts attempt to set certain serial port factors (speed and hardware handshaking) that do not apply to USB.  These might be ignored or might cause the scripts to fail! It may have trouble hanging up the line.

The reasons to try are:
  1. Should improve throughput on all connections above 28.8Kbps.  (Runs serial port at the highest speed available, tries 203400, 115200, and 57600)
  2. Will fix certain problems of compatibility with 3Com digital (ISP) modems.  (later fixed in the 2.0 apple upgrade)
  3. Captures most of the diagnostic information of the &v1 command.
  4. Avoids the lack of guard time on the + + + escape sequence.
  5. More detail to the Activity Log.

Apple 56k int(V.90) (Download)
Apple 56k int(V.34) (Download)
These scripts include a minor bug fix in the detail capture over the ones posted to info-mac in 2000. They also set touch tone times to 70ms instead of the default 95ms, most modems built for the US default to 70ms.  Result, faster dialing, 1/2 sec for ten digits - not much but is seems faster.
After unstuffing the .hqx and the resulting .bin, place the files in the folder called Modem Scripts which is in the folder called Extensions which is in the Systems folder.  Finder does not know where to place these by just dropping in the Systems folder, you must put them in the right place.  Open the Modem control panel and select the new script from the list.  You must close and save for the change to take place.  If the new script does not work open the control panel and select the original script, close and save.  To get the most of the diagnostic information open the Remote Access panel, click options, click the Connections tab, check the verbose logging box, make sure the logout out after idle is set the way you want, click OK.  After a remote access disconnects and returns to idle the Activaty Log may be read for clues as to how the session went.  Among the items of interest are TERMINATION REASON, LAST RX rate, and Line QUALITY (a three digit number the lower the better). A sample log on a line too far from the CO for a reliable V.90 connection.
g w b a l t z e l l at yahoo dot com
feedback (good and bad) about these scripts welcome, but the scripts aresnot guaranteed.
Notes:
Spiral of Death on the US Robotics modem (V.90) is the common condition where the modem retrains to a lower speed and never retrains up.  This contiues until it can go no lower and just disconnects.  I do not know about V.92 modems but since it was never acknowledge or fixed in the V.90 it may still exist.  However, these do have better diagnostics for certain line conditions.

CO - Central Office - the building that the phone lines run into.  Several in larger cities (central?).
DSL - Digital Subscriber Line
ISDN - Integrated Services Digital Network - A very old AT&T protocol (before the breakup in 1984) that most phone companies don't know how to set up and over charge for.  Avoid if possible.
ISP - Internet Service Provider
Line length - the total length wire from the CO to your modem plus any other wiring attached (like continuing down the street though bridging clips in the local distribution box, and wiring in you own home).  Distance is NOT as the crow flies.
Loading coil - a phone line device to boost voice volume but reduces high frequencies.  Usually used on lines longer than 18,000ft or wiring smaller than 24 guage.
Modem - Modulator/Demodulator.
MOV - Metal Oxide Varistor - one of several types of surge suppresors.
Noise - in the context relating to modems is either a radiated signal (like radio waves) that might be generate by fluorescant lighting, motors with brushes (vacuum cleaner, mixer, blender, food processor, drill, hair dryer and possible others) or a magnetic field near the phone wiring or modem (fluorescant ballast, power supply of most electronic equipment, all motors including fans, older ringers in phones).  Also a burst of noise is generated when anything electrical is turned on or off.
pad - a device to attenuate (reduce) signal stength, comes as analog or digital.  Some digital pads may reduce modem speed.
PAD - (not to be confused with pad above) Packet Assembler/Disassembler
POTS - Plain Old Telephone Service.
PSTN - Public Switch Telephone Network.
Repeater - an amplifier used in phone lines.
TELCO - Telephone Company.
USB - Universal Serial Bus.

Software Modem - Called "host based", controllerless, soft, or winmodems - a modem that uses the main computer processor to do error correction and data compression, as well as command processing.  i.e. - cheaper!
Hardware Modem - controller based - uses its own processor to do error correction and data compression and command processing.  i.e. - better!

V.90 or V.92 connections are NOT possible unless the phone company switch (the thing that routes the calls) is capable of ISDN (whether they offer ISDN or not)! These higher speeds depend on the signal coming from the phone company being generated (one time only) from a digital to an analog one.  Multiple D/A and A/D conversion can only support V.34.  The connection all the back to the ISP must be digital! Long distance dialup may or may not work at V.90 (or V.92) because of this.

All Apple 56K internal modems I have seen are Hardware Modems (by looking up the chip set - the only real way to tell).
The Apple modem before firmware update 2.0 tried to test the line for V.90 compatability, when it did this with a 3Com modem on the ISP side it would always fail and drop to a V.34 connection (slower).  The documentation and fix is on the 3Com site.  The fix was to turn off this test in the Rockwell (now Conexant) chip with the s202=32 command.  Version 2.0 firmware doesn't reject this command so it was left in the script.  Conexant long ago lost the documentation of this command.

Replacement lighted dial transformer at Mike Sandman's site (bottom of page).  Top of page has history and rest of site has useful info. and devices

The + + + command is to get the modems attention (put it into command mode after it is connected) which is fine as long as you don't send + + +. There is supposed to be a two second delay before and after to allow the + + + to be sent as part of data.  There is a patent on this delay and most chip makers do not want to pay for it and do not put it in their firmware.  They do usually put it in the manual! The original Apple scripts I started with did not have this delay so if it had been in the chip it would not have worked! I think most manufactuers just hope you don't send 3 plus together very often.

Chip manufactuers history.
  1. Rockwell spun off to Conexant.  Documentation on their web site is only for current products!
  2. AT&T Microelectronics combined with Bell Labs to be Lucent Technologies and then spun off again as Agere Systems.  Will likely not be spun off as part of the higher speed products (like DSL) into Mindspeed.
  3. US Robotics was bought by 3Com then sold to another company now doing business as US Robotics, chips were made by TI (Texas Instruments) current chip maker not known.
These three are the only remaining widely used chip sets.  Motorola makes (made?) a chip set but even they didn't use it in their own modem.
The D.C. Hayes company (which introduced the command based modem in 1981) is long gone; assets were bought by ZOOM Telephonics.
Before this you either dialed the number on a phone and then connected the modem or used TWO expensive serial ports to connect to TWO expensive boxes; the modem and the dialer.
Wiring tips: The point at which the phone line switches from phone company responsiblity to yours is called the demarc (demarcation).  Older lines have a simple lightning arrester, newer ones have a Network Interface Box which also includes a modular plug and jack set so that the house wiring can easily be disconnected and a phone be plugged in for testing.
Network Interface Box
Network Interface Box
Important Warning IMPORTANT - NEVER test or work on phone lines when there are storms in the area!
Important Warning IMPORTANT - NEVER work on inside phone lines unless disconnected at the network interface box (ring voltage exceeds 90VAC)!
Try to keep new wiring away from fluorescant fixtures and AC wiring (2ft. min., 4ft. prefered).  If it must cross AC wiring do so at a 90 degree angle and as much distance as possible.
Color codes below are guides, do not assume the person that installed the wiring followed the standards.
If you are rewiring yourself follow the standards, the person that has to troubleshoot later (it may be you!) will thank you.
It is essential that pairs (blue, blue/white) be used.  The fact that each pair is twisted is what gives the wires noise immunity!
Use only solid wiring for in house, stranded is intended for patch (short) cords.
There are two terms often found in dealing with wiring, these are TIP and RING which are named after the two parts of the old operators phone plug.  RING in this case has nothing to do with the phone ringing.
Operators Phone Plug
TIP is positive and RING is negative. Most modern phone equipment is not sensitive to polarity (switching of the two wires called TIP and RING).  The one known old AT&T phone which is sensitive to polarity will work in all respects except the buttons will NOT generate tones (No damage to the phone, correcting the wiring fixes the problem).
Old 4 wire colors:
  • Line one TIP - Green
  • Line one RING - Red
  • Line two TIP - Black
  • Line two RING - Yellow
New 8 wire colors:
  • Line one TIP - Blue/White
  • Line one RING - Blue
  • Line two TIP - Orange/White
  • Line two RING - Orange
  • Line three TIP - Green/White
  • Line three RING - Green
  • Line four TIP - Brown/White
  • Line four RING - Brown
Wiring for each location in the home should run all the way back to the Network Interface Box and NOT daisy chained from room to room.
More detail wiring info.  at Phone-Man including diagrams.
I do not recommend rewiring old type lighting arrestor demarcs (because you can't disconnect it) but the wire coming from the pole that has a ridge on it is supposed to be RING.

Cat. 5e wire is usually available at Lowes, Home Depot, and a large number of others.
Apple - Remote Access: Modem Script Basics
Apple - Remote Access: CCL Command Glossary
Apple - Remote Access: CCL Result Code Listing
Apple Modem Script Generator 1.0a1 Document and Software (scripts generated by this normally need a lot of editting!)

Apple - Internal Modems: How To Determine Model Installed
Apple Internal Serial port Modem manual
Apple Internal USB Modem manual

Apple - Troubleshooting Phone Line Issues That Affect Modem Connections
Apple - 56Kbps Modems: Getting The Fastest Connection

Apple - Power Mac G4: Choosing Between Internal Modem Scripts

56k.com Modem Central
3Com white paper on 56K modems (no longer on the 3Com site)
56Kbps Data Transmission across the PSTN by P. Michael Henderson (in .pdf Acrobat)
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g w b a l t z e l l at yahoo dot com
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