Telephone apparatus system
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
Jul 23, 1991
Grant Date -
N/A
app pub date -
Aug 22, 1989
filing date -
Aug 24, 1988
priority date (Note) -
Expired
status (Latency Note)
Importance
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.
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