| DK14711C (en) | | Sound amplifier for Microphones, Hearing and Speech tubes and the like. |
| CA124423A (en) | | Sound amplifier |
| ES48511A3 (en) | | Improvements in the construction of speakers or sound amplifiers. |
| DK11675C (en) | | Voice plate for Accordions and the like. |
| CA134674A (en) | | Sound intensifier for telephone mouthpieces |
| DK11426C (en) | | Electric Sound Amplifier. |
| DK13434C (en) | | Device for Amplifying the Effect of Sound Waves by Telephone Speeches. |
| FR371113A (en) | | Sound amplifier for megaphone, acoustic tubes, telephones, etc. |
| CA123767A (en) | | Sound intensifier |
| FR401442A (en) | | Sound amplifier telephone transmitter |
| FR419817A (en) | | Acoustic membrane |
| DK23140C (en) | | Device for amplification and reproduction of sound waves. |
| DK13132C (en) | | Diaphragm for Acoustic and Musical Instruments. |
| DK15022C (en) | | Apparatus by which the sound of speech machines and the like can be conducted and propagated. |
| FR380131A (en) | | Speaker acoustics |
| DK14614C (en) | | Case for Cigar Tubes, Cigarette Tubes and the like. |
| DK15226C (en) | | Transposition device for cross-stringed Pianos, Grand Pianos and the like. |
| FR477210A (en) | | Microphone development |
| CA115776A (en) | | Sound reproducer |
| GB191100289A (en) | | Improved Sound Post Setters for Violins and the like. |
| CA124118A (en) | | Microphone |
| AU439256B2 (en) | | Amplifier |
| DK11192C (en) | | Lining for Speech and Hearing Tubes by Telephones. |
| DK14094C (en) | | Multi-pressure bellows for organs and the like. |
| DK13646C (en) | | Telephone hearing aid. |