a portable printing data entry terminal device includes a portable data entry terminal unit which has a display and keyboard for manual entry of data and control instructions . the data entry terminal unit is powered by a rechargeable battery pack which is housed within the terminal unit . a printer unit is mounted to one end of the data entry terminal unit . the printer unit has its own battery pack to power the printing function . an electrical and data interface between the terminal and printer units routes data to the printer unit for information to be printed . the interface also routes communication and power lines through the printer unit to external connectors disposed at one end of the printer unit . the printer power , though contained within the printer unit , is controlled by the data entry terminal unit to be selectively turned off . controlling the printer power to be turned on only when information is to be printed tends to equalize the discharge cycle of the terminal and printer batteries .