FIELD: radio communications. SUBSTANCE: portable radio communication device operating in first and second modes has receiver, controller, and mode control unit. Receiver functions to receive indexed information messages. Controller stores list of unmasked information fields and is coupled with receiver. It also decodes indexed information message, shapes index part of decoded indexed information message, and generates mode control curve on the basis of index part and list of unmasked information fields. Mode control unit is connected to controller for controlling first and second modes of portable radio communication device in compliance with mode control curve. EFFECT: provision for energy conservation when long messages are transmitted to portable radio communication device. 15 cl, 8 dwg
