Issued Patents 1989
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4855653 | Obstruction detection in automatic portal control apparatus employing induction motor power factor | — | 1989-08-08 |
| 4796011 | Gate operator with persistant, audible warning signal | James S. Amtmann | 1989-01-03 |