Cordless telephone set

Claim 2

A portable telephone set as claimed in claim 1, characterized in that said D.C. signal detection means comprises current detection means (23) for detecting a D.C. current supplied from the battery charger.

Claim 3

A portable telephone set as claimed in claim 1, characterized in that said D.C. signal detection means comprises voltage detection means (43) for detecting a D.C. voltage supplied from the battery charger.

Claim 4

A portable telephone set as claimed in claim 1, characterized in that said power supply line setting means comprises switch means (25), connected between said part of the communications means and the battery charger, for connecting said part of the communications means and the battery to each other when said D.C. signal detection means detects the D.C. signal.

Claim 5

A portable telephone set as claimed in claim 4, characterized by further comprising a power supply line supplying the electricity from the battery charger to said switch means.

Claim 6

A portable telephone set as claimed in claim 1, characterized by further comprising switch means (25) for connecting said battery and said part of the communications means when said part of the communications means detects a call.

Claim 7

A portable telephone set as claimed in claim 6, characterized by further comprising hold means (11, 24), coupled to said switch means, for holding a connection between said battery and said part of the communications means until said portable telephone set is put offhook in response to receipt of the call.

Claim 8

A portable telephone set as claimed in claim 1, characterized in that: said D.C. signal detection means comprises a photocoupler (231) comprising a diode passing a D.C. current from said battery charger and a transistor which is turned ON when the D.C. current passes through said diode; and said power supply line setting means comprises switch means (25), coupled to said photocoupler, for connecting both the battery and the battery charger to said part of the communications means when said transistor is turned ON.

Claim 9

A portable telephone set as claimed in claim 1, characterized in that: said D.C. signal detection means comprises a transistor (51) which is coupled to said battery charger and turned ON in response to said D.C. signal; and said power supply line setting means comprises switch means (25), coupled to said transistor, for connecting both the battery and the battery charger to said part of the communications means when said transistor is turned ON.

Claim 10

A portable telephone set as claimed in claim 1, characterized by further comprising charging circuit means (17), coupled to said battery, for generating a charging current from the D.C. signal supplied from the battery charger and for supplying said charging current to said battery.

Claim 11

A portable telephone set as claimed in claim 10, characterized by further comprising a bypass line which bypasses said charging circuit and connects the battery and the battery charger to each other.

Claim 12

A portable telephone set as claimed in claim 11, characterized by further comprising a first diode (28) provided in said bypass line so that a current from the battery is prevented from flowing to the battery charger.

Claim 13

A portable telephone set as claimed in claim 12, characterized by further comprising a second diode (27) provided in said bypass line, said second diode having an anode connected to the battery and a cathode connected to a cathode of said first diode.

Claim 14

A portable telephone set as claimed in claim 1, characterized in that said power supply line setting means comprises: switch means (25) for connecting both the battery and the battery charger to said part of the communications means in response to a control signal; and logic gate means (24), coupled to said part of the communications means and said D.C. signal detection means, for generating said control signal from an output signal of said D.C. signal detection means which is generated when said D.C. signal detection means detects the D.C. signal and an output signal generated by said part of the communications means in response to receipt of the call.

Claim 15

A portable telephone set as claimed in claim 14, characterized by further comprising a power supply line which supplies the electricity generated by the battery to said logic gate means.

Claim 16

A portable telephone set as claimed in claim 1, characterized in that: said portable telephone set comprises a switch (25) which is provided between said battery and said communications means and which has a first mode, a second mode and a third mode; the electricity generated by said battery is supplied to said communications means when said switch is set in the first mode; the electricity generated by said battery is supplied to only said part of the communications means when said switch is set in the second mode; and the electricity generated by said battery is not supplied to said communications means at all when said switch is set in the third mode.

Claim 17

A portable telephone set as claimed in claim 1, characterized by further comprising terminals (16) to which the battery charger is connected.

Claim 18

A portable telephone system comprising: a portable telephone set (1000, 1000A, 2000, 2000A); and a host device connected to an exchange via a transmission line and connected to said portable telephone set via radio channels, said portable telephone set comprising: communications means (1, 2, 7, 8, 9) for communicating with another cordless telephone set via the host device and the exchange, said communications means comprising a part which detects a call received via the host device and indicates receipt of said call; a battery (15) generating electricity necessary to operate the cordless telephone set; D.C. signal detection means (100, 300, 23, 43) for detecting a D.C. signal supplied from a battery charger when the battery is coupled to the battery charger and charged thereby; and power supply line setting means (200, 24, 25), coupled to said part of the communications means and said D.C. signal detection means, for establishing a power supply line for supplying the electricity generated by at least one of the battery and the battery charger to said part of the communications means when said D.C. signal detection means detects said D.C. signal.