KEY TELEPHONE SET PROVIDED WITH FUNCTION HANDLING POWER FAILURE

摘要

PROBLEM TO BE SOLVED: To provide a key telephone set provided with a function against power failure that can use an external ISDN line even on the occurrence of a power failure as well as at application of power of a master set. SOLUTION: This telephone set 40 (50) that is connected to a master set 20 to which an ISDN wire line is connected and is provided with a CPU 41 (51), a master set interface 42 (52), a telephone set section 44 (54) or the like, is provided with an ISDN interface 42B (52B) directly connected to the ISDN wire line. The key telephone set 40 (50) uses the master set interface 42 (52) at application of power to the master set and uses the ISDN interface 42B (52B) on the occurrence of a power failure in the master set. The key telephone set 40 (50) is in operation by a DC power supply from the master set 20 at application of power to the master set and in operation by power with a limit from the 1 ISDN wire line on the occurrence of a power failure in the master set.