| Number | Name | Date | Kind |
|---|---|---|---|
| D191581 | Scharfenberg et al. | Oct 1961 | |
| D198913 | Smith | Aug 1964 | |
| D233152 | Knutson | Oct 1974 | |
| 3588795 | Linardos et al. | Jun 1971 | |
| 4413518 | Jones | Nov 1983 |
| Entry |
|---|
| Practical Electronics, 5/81, p. 48, Digisounder. |
| Powerboat & Fishing Instruments Buyers Guide, 1982, pp. 43-53, Depth Sounders. |