Issued Patents All Time
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4567333 | Electronic tone ringer with distinctive signaling circuitry | David M. Embree, David C. Goldthorp, David R. Vogelpohl | 1986-01-28 |
| 4491691 | Electronic tone ringer | David M. Embree, David C. Goldthorp, David R. Vogelpohl | 1985-01-01 |