| # | Country | Total Patents | |
|---|---|---|---|
| #1 | United Kingdom | 3 | |
| #2 | Australia | 1 | |
| #3 | Brazil | 1 | |
| #4 | Canada | 1 | |
| #5 | Denmark | 1 | |
| #6 | EPO (European Patent Office) | 1 | |
| #7 | Spain | 1 | |
| #8 | Hong Kong | 1 | |
| #9 | Ireland | 1 | |
| #10 | Israel | 1 | |
| #11 | India | 1 | |
| #12 | Mexico | 1 | |
| #13 | Norway | 1 | |
| #14 | New Zealand | 1 | |
| #15 | Portugal | 1 | |
| #16 | Singapore | 1 | |
| #17 | United States | 1 | |
| #18 | South Africa | 1 |
| # | Industry | |
|---|---|---|
| #1 | Audio-visual technology | |
| #2 | Telecommunications | |
| #3 | Consumer goods |
| # | Technology | |
|---|---|---|
| #1 | Loudspeakers and microphones | |
| #2 | Sound-producing devices | |
| #3 | Telephonic communication |
| # | Name | Total Patents |
|---|---|---|
| #1 | Charlesworth David Valentine | 11 |
| #2 | Smith Derek Frederick | 10 |
| #3 | Charlesworth David V | 2 |
| #4 | Smith Derek F | 2 |
| #5 | Charlesworth D V | 1 |
| #6 | Smith D F | 1 |
| Publication | Filing date | Title |
|---|---|---|
| GB2130843A | Electro-acoustic transducer and adaptor therefor | |
| GB2106748A | Telephone transducers | |
| IE822150L | Improvements in or relating to telephone transducers | |
| GB2078044A | Acoustic resistances |