Most connection problems are a result of "Noise on the Line" caused by wiring problems either at your home or office or by the relay stations down the street. Often is the case a computer can't connect, then the same computer is taken to another location and the connection is made with no problems. 

Symptoms of wiring problem.

One of the primary indications of a wiring problem is the failure to connect at the full baud rate of the slowest modem. This is especially true when connecting to a digital modem at the far end, since the only analog portion is that between your modem and the local phone company switch.

A phone line that connects at various rates depending upon the weather. Slower when wet/damp, faster after dry spells probably indicates a problem off premise. While a consistently slow connection indicates online problems.

Identification of causes.

The faster the baud rate of the modem, the more susceptible it is to noise caused by poor physical wiring connections, inducted noise from local 110 and 220 volt power wiring, motors, and Flo-resent lights. Also hi-fidelity amplifiers and television sets generate strong electrical fields, these fields can generate considerable noise on the phone lines.

Also, since the modem at your end lives in an analog world, capacitance on the phone line is changed by the number of extension phones, fax machines, answering machines attached to the line.

Solutions to wiring problems.

Always use premise type of wiring to the wall nearest the modem. (Premise wiring is a round cable, normally with 2 pair of solid copper wire, each pair twisted.)

The twisted wire helps defeat exterior electrical fields. The greater the number of twists per inch the better the rejection of these electrical fields.

Keep the use of flat phone wire to an absolute minimum. The modem normally comes with a flat cable with an RJ-11 connector at each end. The length of this wire is a good guide to a practical maximum length. Use of longer lengths or intermediate connectors to extend this length with additional lengths of flat cable are prime source for additional phone line noise.

A small toroid (a donuts made of ferrous metal), with 3 or 4 wraps of the flat wire thought the hole will help common mode noise. This should be done within 6 or 8 inches from the modem end of the flat cable.

The premise wiring itself must be sound. Staples use to hold the wire in place piercing the outer casing is a common problem. Connection blocks where extension phones lines are split off can be a source of problems if the location is wet (or has been wet). Even just open copper wire will corrode over time, increasing the resistance of the wire and changing its capacitance.

And of course too many extension phones, fax machines, and answering machine will also change the capacitance of the phone line.

Lastly. Please be sure that the modem is the very first item from the wall. All other phones, answering machines, and fax machines connected to this extension must be connected to the 2nd connector in the modem. A splitter is a sure fired problem point.

If all the above has been checked and you are still having problems. Then the simplest thing to do (and the cheapest ) is to change the modem. Different modems deal with the noise in different ways.

Average modems cost between $39.00 to $99.00 

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