Multiplex communications – Wide area network – Packet switching
Patent
1989-08-22
1991-07-23
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
3701101, 379 93, 379 94, H04M 1100
Patent
active
050349481
ABSTRACT:
A telephone system connected to an ISDN and a public service telephone network (PSTN) includes ISDN and PSTN interfaces and allows connected telephone sets to communicate with the both the ISDN and PSTN through a telephone apparatus main body. When the telephone apparatus main body becomes inoperative due to a power failure or the like, the ISDN or the PSTN is directly connected to one of the telephone sets. The connected telephone set receives operating power from the directly connected ISDN or PSTN, and can serve as a telephone set exclusively for the connected ISDN or PSTN.
REFERENCES:
patent: 4746986 (1988-05-01), Tanigawa
patent: 4794595 (1988-12-01), Ohyama
patent: 4893331 (1990-01-01), Horiuchi et al.
Mizutani Koichi
Ozawa Isamu
Canon Kabushiki Kaisha
Hsu Alpus H.
Olms Douglas W.
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