Modem Installation

There are differing setup requirements for modems so the best advise is to carefully read the installation instructions that come with the modem. Internal modems cause the most confusion and aggravation so let’s look at some considerations.

Most computers come with two Com (Serial) ports. If you use a Serial mouse, it is normally installed on Com1, you could disable Com2 in your BIOS and use Com2 for your modem, but that is throwing away a port that you could use for other purposes, you would use Com2 for an external modem. If you use a USB type mouse Com1 would be open and available Remember we said earlier that an internal modem is it’s own port, so it can become either Com3 or Com4. If you have a mouse on Com1, do not use Com3 for the modem. Com1 normally shares the same IRQ as Com3. Com2 shares an IRQ with Com4. We said normally because although Com1 & 2 are sometimes hardwired, com3 & 4 can also be placed on IRQ’s 2, 5, 9, and 11. Of course, you only have 15 IRQ’s in total and most will be needed for other devices. The following are the usual hex addresses and ports used for internal modems:

Port Hex IRQ
Com1 3F8 IRQ4
Com2 2F8 IRQ3
Com3 3E8 IRQ4
Com4 2E8 IRQ3

Most modems have jumpers or switches to set the Com port, Plug and Play modems will also have a PnP setting that will let Windows assign the port and hex address. Some modems are software configurable. If your modem and OS are Plug and Play it is usually OK to let Windows assign the IRQ and port, otherwise set the modem for the IRQ and port you want to use. If your mouse is not on Com1, use Com3 or Com4. If your mouse is on Com1, use Com4. Most modems come already set to Com4 as a default.

Choosing either a PCI modem or an ISA modem has no effect on modem speed, either slot is more than fast enough for a modem. An advantage to a PCI modem is that PCI devices can sometimes share the same IRQ.

As with any add in card, once you open the computer case you will need to select the slot you will use. Turn OFF the power and unplug the power cord before working inside the case. ISA slots are usually black and in the rear left hand corner of the motherboard, PCI slots are usually white and shorter than the ISA and slightly farther away from the rear panel. Metal slides in the rear panel line up with each slot. Remove the slide for the slot you intend to occupy, it will either be held in by a screw, or the breakout type which can be removed by prying them with a screwdriver blade and then flexing back and forth until it snaps off.

Carefully line up the card edge with the slot and firmly press it straight down into the slot, you should not need excessive force. When the entire edge of the card is evenly seated, secure the card with a retaining screw at the top of the metal bracket. There will be two RJ11C modular telephone jacks exposed on the rear of the card where it shows through the rear panel, one is marked “LINE” and you will run a telephone cord from it to a nearby telephone wall jack. The other jack will be marked “SET” or “PHONE” and you may plug a standard analog telephone into that jack if you wish.

Unlike some devices for which you can use the drivers in Windows, you will want to use the drivers that came with your modem. When you turn on the computer and Windows finds the modem select the Have Disk option and put the driver CD or diskette into the proper drive and follow the instructions that came with the modem to install the driver inf file. Most manufacturers frequently release updated drivers so it pays to check their web sites for new versions even with a brand new modem.

Testing the Modem

To test your modem, go to Start/Settings/Control Panel and double-click on the Modem icon. A window will open that should show your modem by name, click on the Properties button and a new window will show what port it is on, there is also a slider to set the volume level of the speaker mounted on the modem card. Below that is a box for maximum speed, set the speed to 115,200 for a 56K modem and click OK. Next click on the Diagnostics tab and in the window that opens click on the Driver button, a box will tell you the driver that is installed. Click OK and then click on the More Info button, a box will say it is communicating with the modem and a results box should report the test results.


If for any reason the diagnostics fail, exit back to Control panel and double click on the System icon, then on the Device Manager tab. There should be a listing for Modem, click on the + in front of it and you should see your modem listed. Look also at the listing for Ports, click on the + and it should show the port your modem is installed on. If either of these are missing, or if there is a question mark (?) or exclamation point (!) in front of the item there was a conflict in the installation. Remove all references to the modem, and shut down the computer via Start/Shutdown, turn off the power for at least 5 seconds and then reboot and go through the detection and driver installation again being sure to follow the manufacturers instructions exactly. PCI modems can be slot sensitive, if computer fails to see or properly set up a PCI modem try putting it in another slot.


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