Setting up the Infra Red hardware on the PC
Inbuilt Infra Red (eg on a laptop)
Getting IrDA to work properly at all can be problematic.
One common symptom after all the drivers have been set up is the message from Windows ‘Cannot search for devices because other infrared devices are operating nearby'. This is supposed to indicate that some interference is being encountered, but in my case it turned out that my laptop was using its built in FIR (fast infrared) hardware which seemed incompatible with my mobile phone (and with an HP printer that I was also, luckily, able to test with).
My laptop hardware setup screen in the BIOS has an option to select the on-board electronics to operate as FIR or SIR (serial Infra Red, much slower but plenty fast enough for a GSM mobile phone service). Anyway, I selected SIR in the laptop hardware set up and disabled FIR.
(I do not suggest that you do this unless you're very comfortable with fiddling at this BIOS level.)
Hints from DELL and IBM users I have no direct experience of DELL or IBM machines. A DELL user emailed some advice suggesting that some DELL machines, and quite possibly others, have the IrDA ports disabled in the BIOS, by default. IBM machines are described in some newsgroup postings as requiring a switch in the BIOS of one of the COM ports to IrDA use before the in-built IrDA port becomes active.
External Infra Red (eg, USB or serial port ‘dongle’ or 'adaptor')
Serial ports can only operate up to 115kbps, and will only support Serial Infra Red, SIR. Nevertheless, that is fast enough for a mobile phone connection which normally operates at 9.6kbps, with some recent services named HSCSD offering from 14.4kbps to 43.2 kbps (look here for some useful information on faster services). GPRS is becoming available (if expensive in the UK, at least) and operates at up to 48kbps. For many users it will be simpler to plug a device into a serial port, than to remove the covers, and add a device to the computer's motherboard, possibly necessitating some BIOS setting or even an upgrade.
I have installed the MA600 device on both an old laptop under W95 using COM1, and on a modern desktop machine under W98SE using COM2. I chose the MA600 because it seemed to be favoured by several contributors to the uk.telecom.mobile Usenet newsgroup. I checked several alternatives which were listed on part of the IrDA hardware page , but rejected most of them because either the manufacturers' did not seem to support them, or they were not available widely in our retail stores or mail order. The MA600 met both my criteria. The MA600 was described on its manufacturer’s website, http://www.mobileaction.com.tw/EnProd/EnProd.htm , where some updated drivers are also available together with some potentially handy software for synchronising phonebooks on a mobile phone. The MA600 comes with a CD and the supplied drivers worked perfectly on both my systems. If you have an older CD, then use the updated drivers from the manufacturer's website.
Recently, the manufacturer has withdrawn this product, replacing it with a USB product, MA620. I have no expereince of this.
Motherboard adapter
Many motherboards are built to a 'standard' design, and include the electronics to accommodate a motherboard based Infra Red device. One advantage of a motherboard device, compared to a serial port device, is that it may operate at up to 4Mbps, (FIR), and could also be used for other functions such as interconnecting with a laptop.
Installing a motherboard device may require changes to some BIOS settings and possibly a BIOS upgrade, both of which are straightforward if the user is confident of making changes at that level.
The Infra red transceiver (transmitter and receiver) has to be obtained, and is on the end of a cable. The other end of the cable plugs onto a 'header' socket on the motherboard. To avoid cables loosely dragging through the cover of the PC, the connection is best made via a connector (also provided in the adapter kit, hopefully) that can be mounted on the outside of the PC cover or mounted on one of the vacant slot locations. That's the principle, anyway.
I have had no experience of this. I would welcome any suggestions for inclusion of information here, or a link to another website, which describes how it has been done.