signals being recorded or played back by vibration of a stylus in two orthogonal directions simultaneously

Full Title

Transducers of moving-armature or moving-core type (acoustic diaphragm of magnetisable material directly coacting with electromagnet H04R13/00) > Gramophone pick-ups using a stylus; Recorders using a stylus > signals being recorded or played back by vibration of a stylus in two orthogonal directions simultaneously