| Number | Name | Date | Kind |
|---|---|---|---|
| 4680729 | Steinhart | Jul 1987 | |
| 4932021 | Moody | Jun 1990 | |
| 5003595 | Collins et al. | Mar 1991 | |
| 5553121 | Martin et al. | Sep 1996 | |
| 5598279 | Ishii et al. | Jan 1997 | |
| 5724406 | Juster | Mar 1998 | |
| 5734706 | Windsor et al. | Mar 1998 | |
| 5768356 | McKendry et al. | Jun 1998 | |
| 5818908 | Kaplan | Nov 1998 | |
| 5864605 | Keshav | Jan 1999 |
| Entry |
|---|
| Harry Newton, Newton's Telecom Dictionary, 14th Ed., ISBN 1-57820-023-7, p. 50, Mar. 1998. |