RS-232 was designed for communication of local devices It supports one transmitter and one receiver. This standard uses single ended signals over unbalanced, unterminated wires. Single ended means the signal is sent over one wire with respect to a single ground source. Unterminated means the signal lines do not have impedance matching at the line ends. This interface is useful for point-to-point communication at slow speeds and over short lengths of cable. Most PCs come equipped with one or more RS-232 serial ports.