If you look at the picture above, you will see two slots: a black ISA expansion slot and a white PCI
expansion slot. The problem is that there is only one expansion slot opening available on the back of
the case. With this type of expansion slot you must choose whether you want to use an ISA card or a
PCI card. You can't use both. That's the reason it's called a shared PCI/ISA slot. This is a good
place to use a modem, since modems are available on both ISA and PCI expansion cards. Below is a
picture of an ISA modem.
Notice that the modem has its own speaker. When you connect to the Internet and hear the modem dialing,
it's this speaker that you hear those sounds coming from. Modems convert a computer's digital data into
analog waves, so that it can travel through the telephone lines to another computer. The other computer's
modem then converts these analog waves back into digital data, so that the other computer can understand
it. Modems are rated by how many bits per second that they can receive data. They normally send data
at a slightly lower rate, which is around 48Kbps, (or 48,000 bits per second), for a typical 56Kbps modem.
Just because a modem is rated at 56Kbps does not necessarily mean that it will be able to receive data at
that speed. Phone lines and your Internet service provider also play a big part in how fast your computer
is able to receive and send information via the Internet. Some phone lines are only capable of transmitting
data at 28.8k. For this reason, even though Internet service providers usually offer a 56K connection, you
can only access the Internet at whatever speed your phone lines will permit. Below is a picture of a PCI modem.