RS 449

The EIA RS-449 standard specifies the functional and mechanical characteristics of the interconnection between data terminal equipment (DTE) and conforms to the EIA RS-422 and RS-123 electrical interface standards. specifies a 37-pin and a 9-pin connector; it is not widely used.

RS-449 can be used at speeds up to 2 Mbps, on cables up to 60 meters.

• it is the interface between the computer or terminal equipment and the modem, representing an example of physical layer protocol.
• the mechanical specification considers a 25-pin connector, with all its dimensions well specified.
• the electrical specification considers that to decide if a bit is at 1, it must have a voltage more negative than -3 volts; and for bit 0, that the voltage is greater than +4 volts.
• It is possible to have speeds of up to 20 Kbps and a maximum length of 15 meters of cable.
• the functional specification indicates the circuits that are connected to each of the 25 pins, as well as the meaning of each of them.