DynaLink, Netcom etc. Always look after your modem. Keep it away from strong magnetic fields, heat, moisture and vibration. Taking care of your modem will not only extend it's life but ensure reliable service for many years. External and Internal.
External modems are by far the most popular because of their reliability.
External modems are housed in a box of their own with status lights telling you what is happening at any given point. They are connected to your computer with a cable and have their own power supply. Internal modems are the least reliable residing within the computer and receiving power from the computer. Because Internal modems are hidden from the users view, their are no status lights to indicate what is happening. This can be quite inconvenient if you have unsaved work.