FR797982A
(en )
1936-05-07
Loud speaker
FR749472A
(en )
1933-07-24
Loud speaker
FR776417A
(en )
1935-01-25
Loud speaker
FR771454A
(en )
1934-10-09
Microphone refinements
DK51211C
(en )
1936-02-03
Portable Hearing Aid for Transmitting Sound Waves Through the Bone Structure to the User's Inner Ear.
DK51777C
(en )
1936-06-22
Hearing aid for transmitting sound waves through the bone structure to the user's inner ear.
FR737288A
(en )
1932-12-09
Sound-emitting mechanism imitating the sound of kisses
FR814659A
(en )
1937-06-28
Loud speaker
FR810939A
(en )
1937-04-02
Microphone refinements
FR729878A
(en )
1932-08-02
Improvements to hearing devices
FR751482A
(en )
1933-09-04
Loud speaker
CA326763A
(en )
1932-10-11
Loud speaker oscillatory member
CA321355A
(en )
1932-04-12
Telephone mouthpiece disinfecting device
DK48656C
(en )
1934-04-23
Speaker with Radio receiver and built-in Sound plate transmission.
ES126383A1
(en )
1932-05-16
Apparatus of sound waves.
FR748569A
(en )
1933-07-06
Improvements made to radio equipment with the possibility of connecting pick-ups, microphones or the like
CA323093A
(en )
1932-06-07
Acoustic diaphragm
FR760446A
(en )
1934-02-22
Portable toiletry bag
AU885932A
(en )
1933-01-06
Improvements relating to sound collecting and sound radiating devices
CA325710A
(en )
1932-09-06
Loud speaker diaphragm
CH160186A
(en )
1933-02-28
Sound cinematography device.
FR810205A
(en )
1937-03-18
Improvements to telephone sets with microphone and receiver remote from the user
FR829468A
(en )
1938-06-28
Improvements to telephone sets with microphone and receiver remote from the user
FR759145A
(en )
1934-01-29
Microphone refinements
CA323822A
(en )
1932-07-05
Acoustical device