CPC Main Group H04R 9/00 Transducers of moving-coil, moving-strip, or moving-wire type 6 direct subcodes Child Classifications Navigate with arrow keys, Enter to open H04R 9/02 Details H04R 9/06 Loudspeakers H04R 9/08 Microphones H04R 9/10 Telephone receivers H04R 9/12 Gramophone pick-ups using a stylus; Recorders using a stylus H04R 9/18 Resonant transducers, i.e. adapted to produce maximum output at a predetermined frequency