... 2.4GHz RF LCD screen 21 key buttons audience response system Version availbaleV2.0: interactive response, voting, exam, ... ID range1~180Scalable FirmwareYesNumber0~9CharacterA~Za~zGeneral specification of system 2.4GHz 2-way digital RF technology. LCD ... statistics function, convenient for teacher currently, general evaluation. Stability system, compatibility, it is better combine use with blank board. ...