| Number | Name | Date | Kind |
|---|---|---|---|
| 4935955 | Neudorfer | Jun 1990 | |
| 4969184 | Gordon et al. | Nov 1990 | |
| 4994926 | Gordon et al. | Feb 1991 | |
| 5062134 | Laird | Oct 1991 | |
| 5077607 | Johnson et al. | Dec 1991 |
| Number | Date | Country |
|---|---|---|
| 0360732 | Mar 1990 | EPX |
| 3230609 | Apr 1984 | DEX |
| Entry |
|---|
| Ericsson Review, vol. 61, No. 1, Dec. 31, 1984, Stockholm (SE), pp. 51-58, R. Dietsch "Hotel Communication System". |
| The article "SR100 PBX", Nov. 1987, p. 17. |