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Important Note:
Loss of synch is a a very specific symptom and should not be generalized as simply "loosing internet connection". The easiest indicator of synch (success or loss) is a diagnostic light on the DSL modem. The exact light indicating synch varies among models and manufacturers, however some common examples are shown below.

Motorola 2210 - DSL
Westell 2100 - Ready
Westell 2200 - RDY/SYNC
Westell 6100/327W - DSL
2Wire - Broadband Link or DSL
Netopia 3346/3347 - DSL Sync

Typically, sync loss is a physical issue between the DSLAM and your modem. Start with the easiest (and most common) causes found in Section 1. If the issue is not resolved use Section 2 to determine whether the problem is on the AT&T local loop or your end.

Section 1 - Typical Synch Loss Causes and Cures

1. Make sure the DSL filters are installed properly, present on all devices, and functioning properly. This is probably the #1 reason for many speed related issues. The BellSouth supplied filters have two outputs, one for phones/faxes/etc and the for DSL. It is very important that all phones/faxes/etc have a filter installed. Make sure you have not installed the filter backwards. See the piture below. Filters can also go bad for various reasons so just because a filter is installed properly does not mean it is still functioning properly. To eliminate the filters as a cause of problem remove all filters and POTS devices from every jack in the home. Replace the filters and POTS devices one at a time and check for any changes in synch. You may need to use a cell phone (or separate line) to place an inbound call to your home number to recreate the loss of synch. Replace any filter that is questionable. Home alarm systems also interfere with DSL. To troubleshoot, simply disconnect any line going to the alarm control module (even if you do not currently subscribe to the service) and check your modem. If the alarm is causing issues you can install a special filter designed for alarms systems or call the alarm company for advice.

Correct DSL Filter Installation

Section 2 - Synch Loss Isolation from the NID

1. Pull your modem stats and event logs and save/print them while connected in your normal configuration before you make any additional changes. Reference the guidelines within the modem stats FAQ to determine if your modem stats are good or not. If your stats and logs look good then you probably do not a physical problem and should look elsewhere. Best advice #1: After you have saved the previous logs, clear them and let the modem create new entries specifically for your testing. If your stats are poor you will have to do further troubleshooting by pulling your modem stats from the NID. Best advice #2: Run the test from the NID for as long as possible. You may have an intermittent issue that doesn't show up if you only check for a minute or two. If you are experiencing troubles at a specific time try and test at that time (if possible). Make sure you recheck the modem logs.
2. If your stats are much better at the NID, you have an issue within the house. Double check the DSL filters are correctly installed and functioning. Bypass any surge protectors because some are incompatible with DSL and even if they are compatible, they may have gone bad. Completely disconnect or install a filter on any alarm system. Eliminate any possible sources of EMI (Electromagnetic Interference) near the modem or the phone line. A simple hand held AM radio can also be used to track down noisy electrical problems. Tune the radio to a lower frequency so you hear only static. Pass the radio near the suspected device and if you hear a major change in the amount of static that device may be causing the problems. Check for loose connections and damaged wire if possible. You can eliminate the need to disconnect alarm systems and individual filters completely by installing a homerun. Customers who live in apartments can also install a homerun by using a specialized splitter.
3. If your modems stats are poor at the NID then it could be a local line issue or a bad modem. A call to BellSouth is in order. If they conclude the modem is bad they may replace it if it's still under warranty. If they conclude it is a local line issue they will troubleshoot further. BellSouth may or may not have the ability to fix your line issue. It may be easily fixed by a simple call or a local tech, but it may be a distance problem that is uncorrectable.

Andy Houtz DSL

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last modified: 2009-04-20 10:48:10