| Number | Date | Country | Kind |
|---|---|---|---|
| 7-166340 | Jun 1995 | JPX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4894861 | Fujioka | Jan 1990 | |
| 4924496 | Figa et al. | May 1990 | |
| 5220599 | Sasano et al. | Jun 1993 | |
| 5267307 | Izumi et al. | Nov 1993 | |
| 5546448 | Caswell et al. | Aug 1996 |
| Number | Date | Country |
|---|---|---|
| 347155 | Dec 1989 | EPX |
| Entry |
|---|
| Tatsuhiro Naganawa, et al., "A Study of Audio Commnication Devices for ISDN", 1990 IEEE conference. |
| Andreas Scroter, "SOPHO.sub.-- SET 138x- A new range of ISPBX telephones", Philips Telecommunication review, 1993 Mar., No. 1. |