| Number | Date | Country | Kind |
|---|---|---|---|
| 2650035 | Oct 1976 | DEX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2135394 | Geissen | Nov 1938 | |
| 2955547 | Ebenbach | Oct 1960 | |
| 3135224 | McLean | Jun 1964 | |
| 3877388 | Hall et al. | Apr 1975 |
| Number | Date | Country |
|---|---|---|
| 50109 | Apr 1941 | NLX |
| 575307 | May 1976 | CHX |
| Entry |
|---|
| Siemens Journal No. 11/1966; pp. 800 to 809. |