| Patents for H04R 13 - Transducers having an acoustic diaphragm of magnetisable material directly co-acting with electromagnet (404) | |
|---|---|
| 05/1978 | |
| 05/16/1978 | US4090041 Electromagnetic sonic generator for an alarm |
| 02/1978 | |
| 02/21/1978 | US4075437 Chromium, cobalt, iron, zirconium, aluminum niobium, and/or titanium |
| 04/1977 | |
| 04/05/1977 | US4016376 Concave diaphragm for electro-acoustic transducer |
| 03/1977 | |
| 03/29/1977 | US4015227 Electromagnetic transducer |