Disconnects
U.S Robotics Sportster gets
slower and slower, experiences long pauses in which no
data is sent, or disconnects suddenly
Lucent LT Win Modem disconnects
Macintosh issues
A checklist for troubleshooting
disconnect problems
Disable call waiting
Upgrade firmware, init strings,
and drivers
Try unplugging any devices from
the back of the modem
Try unplugging other telephone
equipment in the house
Try lowering the port speed
Lowering connect speed with
K56flex or K56flex/V.90 modems
"I want call waiting to disconnect
me when I have an incoming call, but it doesn't."
USR Sportsters get slower and slower, and may disconnect
suddenly
This is the x2 version of Spiral Death Syndrome. The fix
in most cases is to add S15=128 to the init string to
disable V.42 hardware error correction. It may also be
necessary to add &K0 to the init string to disable
V.42bis hardware data compression, though this should be a
last resort, as performance will suffer when downloading
non-compressed files.
Lucent LT Win Modem disconnects
1. Try using the init string AT&FX. (See the next
step for instructions.)
2. Set Windows 95/98 Dial-Up Networking to use software
flow control. Here's how:
- Doubleclick My Computer, then doubleclick the Dial-Up
Networking folder.
- Right-click on your connection icon and choose
Properties.
- Click the Configure button.
- Click the Connection tab.
- Click the Advanced button.
- Put a check next to "Use flow control" and select
"Software (XON/XOFF)."
- In "Extra settings," enter "AT&FX".
- Click OK to save changes.
Screenshot
showing these two changes
3. If that doesn't help, you might try lowering your
connect speed to 57600. (The speed setting is on the first
screen when you get Properties on your connection icon.)
This should be a last resort, as it will affect your
download speed somewhat.
Macintosh issues
The Macintosh uses an 8-pin serial port, rather than the
9- or 25-pin port on most other computers. As a result, Mac
modem cables handle DTR differently, and DTR is often used
as a disconnect signal.
The classic symptom of unwanted DTR disconnect on the Mac
is getting knocked offline when receiving a large stream of
data. This may happen during a download, or when issuing a
dir command in a command-line FTP program.
To disable DTR hangup, add &D0 (zero) to the end of
your init string.
A checklist for troubleshooting
disconnect problems
Here's a rundown of the most common solutions for
unwanted disconnects
Disable call waiting
You probably know this already, but you should disable
call waiting. The "click" of an incoming call may disconnect
you, though newer modems have improved error correction that
is less sensitive to this.
In most areas, you can disable call waiting on a
touchtone line by placing *70, in front of the phone number,
like so:
*70,555-5555
If your lines do not have touchtone service, and instead
use pulse dialing, the command is 1170,.
Note that in some areas, the phone company charges you
each time you disable call waiting. Also, some areas use
different commands, or may require you to request the
ability to disable call waiting. If in doubt, call your
phone company.
Upgrade firmware, init strings, and
drivers
Many disconnect problems can be solved by loading a more
recent version of the firmware. Check the firmware
page.
Likewise, having the correct modem init string or driver
installed is important. Check the inits
and drivers page.
Try unplugging any devices from the back
of the modem
Modems have two phone jacks on the back: one is for the
line connected to the wall jack. The other is for plugging
in a telephone, answering machine, fax machine, etc.
Try unplugging your telephone or any other device
attached to the back of the modem. Some devices may cause
problems. For instance, some telephones draw power from the
phone line every 15 minutes to power the circuits that keep
track of speed dial numbers.
Try unplugging other telephone
equipment in the house
It's possible to have too many devices on your phone
lines or extension. Try unplugging extra phones, fax
machines, and answering machines to see if the disconnects
stop.
Try lowering the port speed
Older PCs may have weak UARTs that are not capable of
high speed communications. As a result, you may get frequent
dropped connections and/or poor modem performance due to
resent packets.
To test this, try lowering your port speed to 38400 or
even 19200. If the dropped connections cease, a slow UART
may be the problem. A replacement serial port card should
fix the problem.
For use with a 56K modem, you want at least 16550 UART.
Internal 56K modems should include a 16550 or higher UART on
the card.
Lowering connect speed with K56flex or
K56flex/V.90 modems
Some K56flex owners have found that they can reduce
disconnects by setting a limit on the initial connect speed.
The commands for controlling maximum connect speed are
different for Rockwell-based and Lucent-based K56flex
modems.
On most Rockwell-based K56flex modems
If you normally get disconnected when you connect at
48000, you might try using:
+MS=56,0,9600,46000
If that didn't work, you would try:
+MS=56,0,9600,44000
+MS=56,0,9600,42000
and so on, reducing the maximum connect speed by 2000
each time. Experiment with different numbers to see if lower
numbers result in fewer disconnects.
On most Rockwell-based V.90 or V.90/K56flex
modems
If the modem supports V.90, use the +MS=12 command (see
above for instructions):
+MS=12,0,9600,46000
On Lucent-based K56flex modems
The S38 command can be used to control the maximum
connect speed. The values between 2 and 14 set the maximum
speed between 32K and 56K. So, if you normally get
disconnected when you connect at 48000, you would try:
S38=9
to set the maximum connect speed to 46000. If you still
get disconnected, you might try:
S38=8 (for 44000)
S38=7 (for 42000)
and so on.
"I want call waiting to disconnect me
when I have an incoming call, but it doesn't."
For solutions and alternatives, read Daniel
Rosenzweig's Call Waiting and Modem FAQ, right here on
56K.COM.
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