Most telephone lines have background noise, and this can cause modems to make errors when they send or receive data. Parity is a fairly old method to detect some of these errors. (Fancier error detection and correction schemes are available today, such as MNP 5 and V.42.bis.) You can set your communications software to use None, Even, or Odd parity. When you want to dial up to a remote system, you must always select the parity value that the remote system expects.
· Tip: Almost no systems use Odd parity. Most systems that use 7 data bits use Even parity, and most systems that use 8 data bits use None.