| Number | Name | Date | Kind |
|---|---|---|---|
| D107538 | McConn | Dec 1937 | |
| D197279 | Bartley et al. | Jan 1964 | |
| D209208 | Gilbert | Nov 1967 | |
| D225113 | Genaro et al. | Nov 1972 | |
| D247174 | Janda | Feb 1978 | |
| D248102 | Blake | Jun 1978 | |
| D269780 | Doodson | Jul 1983 | |
| D278054 | Vajdaffy | Mar 1985 | |
| D278055 | Vajdaffy | Mar 1985 | |
| 2433295 | Riebe | Dec 1947 | |
| 2948377 | Kennedy | Aug 1960 | |
| 3144513 | Sherron | Aug 1964 | |
| 3247332 | McHugh | Apr 1966 | |
| 3800089 | Reddick | Mar 1974 | |
| 3932709 | Hoff | Jan 1976 | |
| 4182938 | Neumeier | Jan 1980 |
| Entry |
|---|
| All About Telephones; 2nd edition by Von Waterford; .COPYRGT.1983 by Tab Books Inc. |
| Amer. Institute of Graphic Standards, 7th ed. by R. T. Packard; at p. 700, Master Station Intercom: center of top Systems. |