| # | Country | Total Patents | |
|---|---|---|---|
| #1 | Netherlands | 3 | |
| #2 | United Kingdom | 2 | |
| #3 | Switzerland | 1 | |
| #4 | Germany | 1 | |
| #5 | France | 1 | |
| #6 | Italy | 1 | |
| #7 | Sweden | 1 | |
| #8 | United States | 1 |
| # | Industry | |
|---|---|---|
| #1 | Control | |
| #2 | Telecommunications |
| # | Technology | |
|---|---|---|
| #1 | Alarm systems | |
| #2 | Wireless communication networks | |
| #3 | Telephonic communication |
| # | Name | Total Patents |
|---|---|---|
| #1 | Graaf Nicolaas Robert De | 2 |
| #2 | De Graaf Nicolaas Robert | 1 |
| #3 | De Graaf Nicolaas R | 1 |
| #4 | De Graaf N R | 1 |
| Publication | Filing date | Title |
|---|---|---|
| NL8000578A | Person search receiver. | |
| GB2051445A | Surveillance system |