A handheld mobile communications device comprising: a support structure; an antenna mounted on the support structure for transmitting and receiving radio signals; radio signal processing circuitry positioned on the support structure to process the radio signals; a speaker and microphone arrangement positioned on the support structure and operatively connected to the radio signal processing circuitry; a printhead positioned on the support structure to carry out a printing operation; and an interface for enabling interrogation of an authentication means associated with an ink cartridge.