There are two types of modems:
- Consumer voice-grade modems Most off-the-shelf modems are designed to allow PC users to communicate over the voice phone system. The modems employ compatible communication techniques that comply with several standards, most notably the ITU V series standards (previously called the CCITT standards).
- Broadband modems These are modems for nontelephone system connections. A company may set up its own dedicated lines or microwave towers and use broadband modems to achieve very high data rates between those sites.