That Old House and this New Modem

If your 56Kb modem is not connecting at a very high data rate or otherwise belching and burping, it may be due to several factors. A big one could be the wiring in your house. Most houses were wired for voice, long before modems in the home were even thought of; let alone considering running them at a whopping 53,300 bits per second (the maximum allowable on a V.90, 56 Kb modem).


Most houses were, and still are wired in a loop that goes from room to room. Every telephone is simply connected to the same two wires where they were cut and screwed to a terminal block. If the house were wired for two lines, chances are that another pair of wires in the same cable bundle was used for the second line promoting cross talk and further exacerbating the problem for future modem connections.


Over the years the cabling, which wasn’t very good to begin with by today’s standards, deteriorated and the connections became loose and corroded. Phones and other devices may have been added and moved, which may have resulted in unterminated loops and unbalanced pairs. However, this mess may still be adequate for voice operation, but modems are much more finicky than the human ear and brain when it comes to filtering out extraneous noises. When you add a modem to this patched up loop, it is subject to all of these problematic shortcomings that may restrict its operation to only a fraction of the speed for which it was designed.


An easy way to test for this condition, is to take your computer to the D-Mark (the place where the phone line enters the house), and connect your computer at that point, or run a separate cable from the D-Mark to your computer. Then, most importantly, disconnect the house wiring. Now try your modem. If it trains up faster and you get a higher connection speed, you probably have a problem in your house wiring. If it doesn’t improve the connection, then the problem is elsewhere, possibly with your phone company or an incompatible modem at the other end.


However, if this is the case, you can re-cable your house or buy an $85.00 Modem Isolation Switch from CPS in Atlanta. It isolates the house wiring from the modem connection, but it does require that you run a separate cable from the D-Mark to your modem (the lesser of two evils). Try to use good twisted pair cable, not silver satin, and don’t get too close to any electrical wiring or florescent light fixtures. If you use a full Category 5 cable, it may also come in handy in the future if you ever go to xDSL.


You would then simply connect the MIS box to the telephone line at the D-Mark and connect the modem to one of its four RJ-11 "snap in" telephone type connectors and connect the house wiring to another. This will isolate the phone cabling and the modem while they are being used. The nice thing about the unit is that it has two more connectors so if you have a few more modems or a fax or anything else that may benefit from a clean connection, you’ll have a place to connect them too.


A side benefit of this isolation is that it also provides something called barge protection. If anyone picks up an extension or another modem while your modem is on-line, it will not interfere with the modem connection. It also provides an additional level of surge protection for both the phone and the modem.


The company also makes another model for two telephone lines. It has eight modem/telephone connections. It adds the additional flexibility of allowing the phones or modems to grab either of the two lines that may be available when making a call.


You can get further information on these products at