Issued Patents 1989
Showing 1–1 of 1 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4864224 | Measuring method for determining the difference between an A-C voltage and another voltage, as well as a measuring device for carrying out the same | Guenter Roppelt, Herbert Ziegler | 1989-09-05 |