Cordless telephone set

Abstract

Disclosed is a cordless telephone set capable of suppressing power consumption during power failures to lengthen the time for a call. A cordless telephone ( 1 ) receives power supply from a handset ( 3 ) placed on a charging section ( 26 ) of a base unit ( 2 ), during power failures. In order to suppress current consumption of a secondary battery (BT) of the handset ( 3 ), the base unit ( 2 ) instructs a base unit radio section ( 21 ) to be switched to a transmission power-saving mode in which transmission power of the base unit radio section ( 21 ) is reduced down to a level at which no communication error occurs, according to radio wave information transmitted from the handset ( 3 ) and indicates the received signal strength of a radio signal from the base unit radio section ( 21 ) of the base unit ( 2 ), received by a handset radio section ( 39 ) of the handset ( 3 ).

1 . A cordless telephone set which performs radio communication between a handset and a base unit which is provided with an external power supply,
 wherein the base unit includes:   a detection unit which detects the external power supply,   wherein the handset includes:   a battery which provides a power supply to the base unit in accordance with the external power supply detected by the detection unit; and   a display section which displays information regarding at least one of the power supply and the external power supply.   
     
     
         2 . The cordless telephone set according to  claim 1 ,
 wherein the base unit further includes:   a first radio communicating section which performs modulation and demodulation with the external power supply; and   a first control section which controls transmission power of the first radio communicating section,   wherein the handset further includes:   a second radio communicating section which performs modulation and demodulation with a voltage output from the battery,   wherein the first radio communicating section receives, from the handset, radio wave information which indicates a received signal strength of a radio signal which is received by the second radio communicating section from the first radio communicating section, and   the first control section reduces the transmission power of the first radio communicating section in response to the received signal strength indicated by the radio wave information on the basis of the external power detected by the detection unit.   
     
     
         3 . The cordless telephone set according to  claim 2 ,
 wherein the first control section reduces the transmission power of the first radio communicating section down to a level at which no communication error occurs.   
     
     
         4 . The cordless telephone set according to  claim 1 ,
 wherein the handset further includes a second control section which starts up a hand-free call function if the handset is placed on the base unit.   
     
     
         5 . The cordless telephone set according to  claim 2 ,
 wherein the first radio communicating section transmits predetermined data to the handset when the detection unit has detected that a voltage from the external power supply does not exceed a predetermined value, and   the display section displays a state where power supply to the base unit from the external power supply is cut off when the second radio communicating section receives the predetermined data.   
     
     
         6 . The cordless telephone set according to  claim 1 ,
 wherein the base unit further includes a capacitor which receives electricity with the voltage from the external power supply or the voltage from the battery.   
     
     
         7 . The cordless telephone set according to  claim 2 ,
 wherein the cordless telephone set includes a plurality of handsets, and   when any one of the plurality of handsets is placed on the base unit, the first radio communicating section communicates with a different handset which is not placed on the base unit with a predetermined voltage output from the battery.   
     
     
         8 . The cordless telephone set according to  claim 2 ,
 the first radio communicating section transmits predetermined information to the handset on the basis of the external power supply detected by the detection unit, and   the display section performs a display for encouraging a user to place the handset on the base unit when the display section has received the predetermined information by the second radio communicating section.   
     
     
         9 . The cordless telephone set according to  claim 2 , further comprising:
 a switch circuit which cuts off power supply to the first radio communicating section from the secondary battery of the handset placed on the base unit when the detection unit has detected that a voltage from the external power supply exceeds a predetermined value and allows power supply to the first radio communicating section from the secondary battery of the handset placed on the base unit when the detection unit has detected that the voltage from the external power supply does not exceed the predetermined value.   
     
     
         10 . The cordless telephone set according to  claim 9 ,
 wherein the first radio communicating section transmits predetermined information to the handset when the detection unit has detected that the voltage from the external power supply does not exceed the predetermined value, and   the display section performs a display for preventing the handset placed on the base unit from being removed from the base unit when the display section has received the predetermined information by the second radio communicating section and the switch circuit allows power supply to the first radio communicating section from the secondary battery.   
     
     
         11 . The cordless telephone set according to  claim 1 ,
 wherein the display section displays information indicating that the external power is unavailable.   
     
     
         12 . The cordless telephone set according to  claim 1 ,
 wherein the display section displays information for keeping the handset placed on the base unit.   
     
     
         13 . The cordless telephone set according to  claim 1 ,
 wherein the display section displays information that the external power supply is available if the detection unit detects that a voltage from the external power supply exceeds a predetermined value.   
     
     
         14 . A power supplying method which is performed between a handset and a base unit which is provided with an external power supply, the method comprising:
 detecting the external power supply;   providing a power supply from the handset to the base unit in accordance with the external power supply; and   displaying information regarding at least one of the power supply and the external power supply.   
     
     
         15 . A cordless handset which performs radio communication with a base unit, the handset comprising:
 a battery which provides a power supply to the base unit in accordance with a status of an external power supply to the base unit,   a display section which displays information regarding at least one of the power supply and the external power supply.   
     
     
         16 . A power supplying method implemented by a handset which performs radio communication with a base unit, the method comprising:
 providing a power supply from the handset to the base unit in accordance with a status of an external power supply to the base unit; and   displaying information regarding at least one of the power supply and the external power supply.   
     
     
         17 . A base unit which is provided with an external power supply and performs radio communication with a cordless handset, the base unit comprising:
 a detection unit which detects the external power supply; and   a switch circuit which receives a status of the external power supply from the detection unit, and connects to a battery of the handset to receive a backup power supply from the battery of the handset in accordance with the status of the external power supply.   
     
     
         18 . A power receiving method implemented by a base unit which performs radio communication with a cordless handset, the method comprising:
 detecting the external power supply; and   connecting the base unit to a battery of the handset to receive a backup power supply from the battery of the handset in accordance with a status of the external power supply.