Computers and telephones don't really mix. The signals whizzing around inside your PC are made up of streams of rapid, precisely contoured digital pulses. The telephone system -- at least the part that connects your home to the exchange -- is designed to handle comparatively slow, undulating voltages. In order to connect a PC to a telephone line and communicate with other computers it needs a device called a modem. Its job is to translate digital bits and bytes into audible tones, and back again.

Quite honestly it's a wonder that modems work at all, let alone achieve the kind of data transfer speeds that are now possible. However, the fact that modems and Internet connectivity cause so many problems clearly demonstrates that we're dealing with technologies based on compromise. There are fast and efficient alternatives, such as ISDN and the recently launched BT Highway system, however the cost remains prohibitive for the majority of domestic PC users. The bottom line is that we're stuck with modems and analogue telephone lines for a while yet, so we might as well make the best of it. This week we'll look at how it all hangs together, next week a closer look at speeds and standards, what's involved in upgrading, and digital phone lines.

We'll begin with a brief guided tour. Know your modem. There are two sorts used with most desktop PCs, internal models that live inside the PC box and external types that connect to one of the PCs serial ports. External modems are a little easier to deal with when things go wrong, though the fact that they require extra cables and a separate power supply means there are more things to go wrong in the first place… Nevertheless they're easy to replace and the row of winky lights on the front panel means you can keep an eye on it and see whether or not you or your Internet software has disconnected at the end of a session.

Hardware faults are quite rare and normally caused by something fairly obvious like a loose cable or malfunctioning power supply. Internal modems can sometimes work themselves loose from their sockets. Modems are also susceptible to damage by high-voltage spikes coming down the telephone line; if yours stops working after a thunderstorm it has almost certainly been fried by a nearby lightning strike.

One of the reasons connectivity and modem problems can be so difficult to diagnose and cure is because there is so much controlling and operating software spread out all over the place. On most Windows 95 and 98 PCs there are at least four key locations. The main set-up controls can be found in 'Modems' in the Control Panel. A modem's relations with the host PC is handled by Dial Up Networking (see My Computer), Internet Browser software often has its own set of modem controls and there's another set of configuration options in Device Manager, (under System in Control Panel).   

It's worth acquainting yourself with some the settings, maybe even taking a few notes when everything is working properly, so you have a benchmark if things turn nasty. Do not on any account mess with anything and when you open dialogue boxes always close them with the Cancel button, so any changes you may have accidentally made will not be applied.

Start with Modems in Control Panel. Make sure the modem model number and speed listed under the General tab are correct. Click on the properties button, the General tab will show the communications port it is using, the Maximum Speed setting should always be higher than the modem's top speed, it is usually safe to leave it on the fastest 115200bps setting. On the Connection tab under Connection Preferences, Data Bits is almost always set to 8, Parity is None and Stop Bits 1. Now click the Port Settings Button, the 'FIFO buffer…' box (see Jargon Filter) is normally checked on Pentiums and PCs made in the last three or four years. The positions of the two sliders will vary; it's worth trying a lower setting if you are having intermittent problems, such as dropped connections or corrupted data. Go back to the Connection tab and click on the Advanced button and note which items have been checked, they will vary according to your browser software, Flow Control and Hardware RTS/CTS settings are generally enabled.

The next stop is your browser. Look for menu items like Options, Preferences or Internet Options. These will contain some or all of the main settings used for your modem connection. Unfortunately it's impossible to generalise as there too many variations so familiarise yourself with the settings, preferably when everything is working normally. Internet browser software is notoriously flaky; some programs can be very territorial and will not co-exist with rival software. The best advice is to only have one browser on your PC at a time, and when you come to uninstall, make sure every last file fragment is removed. Always use the browser's uninstall utility -- assuming it has one, not all of them do -- or make it a rule never to load Internet access software unless you also have an uninstaller program like CleanSweep or Uninstaller on your system.

There's a lot of information contained in Dial Up Networking and like just about everything to do with modems and Internet connectivity most of it is gobbledegook that really needn't concern the average user, until it goes wrong… Right click on your Dial Up Connection icon and select Properties. Once again, look and take note but don't touch anything, unless you know what you are doing. The Device Manager which lives in the System icon on Control Panel is a good place to check if a sudden problem arises, if you see a yellow-ringed exclamation mark next to the Modem listing then there may be a driver or resource conflict. To resolve it start the Conflict Trouble-shooter utility by typing 'Conflict' in Windows Help.

Next Month: the need for speed, installing a new modem and digital telephone lines




First in first out -- a efficient method of handling data whereby information is processed in the order it is retrieved or stored


Integrated Services Digital Network -- a specialised high-speed digital telephone line for carrying data and high quality speech


MOdulator-DEModulator -- an electronic device that turns digital data into audio tones -- and vice versa -- enabling computer information to be sent down ordinary domestic telephone lines



If your phone is connected to a digital exchange and you have BT Call Waiting or Call Minder services you may experience problems with Internet connections. Windows 95 and 98 can automatically switch the Call Waiting bleeper off before you connect. Open Modems in Control Panel and select the General Tab. Click on Dialling Properties and check the box marked ' To Disable Call Waiting Dial', (or 'How I dial from this Location'), in the adjacent box enter # 43 # (hash 43 hash). You will have to manually switch Call Waiting back on again after you log off by dialling * 43 # (star 43 hash). Call Minder generates a 'stutter' dial tone to let you know you have a message waiting, this does not agree with a lot of modems, so before you go on-line pick up your messages by first dialling 1571.

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