A selector box for switching between RS232 ports is disclosed. A single host terminal is provided and a plurality of channel terminals are provided. In a first mode, a command comes from the host terminal determining which of the channel terminals the host terminal will be connected to. In a second mode, the command comes from a channel terminal requesting access to the host terminal. The device can also be operated in a manual mode where a manual switch performs the connecting function. In the first mode the signal commanding the channel number is part of the transmit data signal of an RS232 interface. In the second mode, the various RS232 interfaces of the channel terminals are all scanned and the first channel to produce a certain signal receives access to the host terminal.