DOT4 is a protocol that allows a device that is part of a multifunction peripheral ( MFP ) to send and receive multiple data packets simultaneously across a single physical channel to other devices on the MFP. All data exchanges are independent of one another so the canceling of one does not affect the others. An example of an MFP is the OfficeJet series from Hewlett-Packard ( HP ), which are devices that contain a scanner , printer , and fax machine all in one. The DOT4 protocol is specified in IEEE 1284.4, an enhancement of the original IEEE 1284 protocol for parallel ports on personal computers (PC). While many MFP devices still use the parallel port, there is a shift to Universal Serial Bus ( USB ) for the high-speed connection of peripheral devices.