All the devices (computers, terminal servers, routers etc.) with separate wires for transmit and receive are DTE (Data Terminal Equipment), while modems are DCE (Data Communications Equipment). When a host is connected to a terminal both are DTE and both use pin 1 for transmit and pin 2 for receive. For the transmit line of one device to connect to the receive line of the other device, pin 1 at one end must connect to pin 2 at the other and vice versa. This is termed a Crossover, and used for EIA 423, 10BASET and FDDI.