Teaching apparatus and instruments; sound recording apparatus; sound transmitting apparatus; sound reproduction apparatus; image reproduction apparatus; data processing equipment; computer peripheral devices; downloadable computer software applications; connected bracelets (measuring instruments); electric cables; printed circuit boards; headphones; printed circuits; electric regulating apparatus; projection screens; video screens; electronic devices for digital display; transmitters of electronic signals; apparatus for GPS (global positioning system)/ apparatus for global positioning system (GPS); loudspeakers; computer hardware; intercommunication apparatus; interfaces (for computers); audio interfaces; software (recorded programs); recorded computer programs; computer programs (downloadable software); projection apparatus; life-saving devices/rescue devices; data processing apparatus; transmitters (telecommunication)