Multi-channel cordless telephone system for maintaining master-slave communication

• US 5,375,163 A
• Filed: 04/20/1992
• Issued: 12/20/1994
• Est. Priority Date: 04/25/1991
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kajiwara, Katsuyuki, Kamimoto, Kouichi
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): Bost, Dwayne D.
• Application Number:
  US07/870,813
• Time in Patent Office: 974 Days
• Field of Search: 379/58, 379/61, 379/62, 455/34.1, 455/34.2, 455/54.1
• US Class Current: 455/464
• CPC Class Codes: H04B 7/2621 using frequency division multiple access [FDMA] H04B7/2615 takes precedence
• CPC Class Codes: H04M 1/72511 Searching for available channels

Abstract

A cordless telephone provided with a master unit and a slave unit which use a plurality of communication channels. In the case where information indicating a currently used channel or a usually used channel, which has been stored in the master unit, is lost due to, for instance, a power failure, the master unit comes to use an initially used channel, which is preset or determined by performing an operation on an identification code, and enters a standby state. At that time, the slave unit uses the usually used channel. However, when it is detected that the slave unit cannot communicate with the master unit, the slave unit calls the master unit by using the initially used channel. Then, the master and slave units come to perform, for example, an exchange of confirmation data by using the initially used channel. Next, the slave unit transmits to the master unit data indicating that the channel used by the master unit should be changed to the usually used channel. In response to the data, the master unit made to use the usually used channel. Consequently, both of the master and slave units come to use the usually used channel and are able to communicate with each other. Thus, the cordless telephone does not require another power source for a backup circuit. Further, the circuit configuration of the cordless telephone becomes simple.

Claims

1. A cordless telephone having a master unit and a slave unit and using a plurality of communication channels for communication between the master unit and the slave unit and employing an identification code indicating that the master unit and the slave trait are coupled with each other, the master unit having first channel changing means responsive to a user'"'"'s operation for freely changing a communication channel currently being used by the master unit, the slave unit having second channel changing means responsive to a user'"'"'s operation for freely changing a communication channel currently being used by the slave unit, storage means for storing information representing a usually-used-channel, receiving means for receiving information, transmitting means for transmitting information, control means for controlling the second channel changing means and the storage means and the transmitting means, wherein the master unit transmits and receives a signal through an initially-used-channel determined from the identification code, wherein, in case the master unit does not normally reply to the slave unit when the slave unit transmits a signal to the master unit, the control means causes the second channel changing means to change the communication channel currently being used by the slave channel into the initially-used-channel and then causes the receiving means and the transmitting means to perform an exchange of data with the master unit through the initially-used-channel and further causes the transmitting means to transmit information representing the usually-used-channel stored in the storage means through the initially-used-channel.

2. A cordless telephone having a master unit driven by an external power source and a slave unit driven by a battery and using a plurality of communication channels for communication between the master unit and the slave unit and employing an identification code indicating that the master unit and the slave unit are coupled with each other, the master unit having first transmitting means for transmitting data, first receiving means for receiving data, first channel changing means for changing a communication channel currently being used by the master unit, first storage means for storing information representing a usually-used-channel, second storage means for storing information representing a predetermined initially-used-channel and first channel setting means for setting the initially-used-channel predetermined according to the identification code and for controlling the first channel changing means in response to a user'"'"'s operation in such a manner to freely change the communication channel currently being used by the master unit, the slave unit having second transmitting means for transmitting data, second receiving means for receiving data, second channel changing means for changing a communication channel currently being used by the slave unit, third storage means for storing the information representing the usually-used-channel, fourth storage means for storing the information representing the predetermined initially-used-channel and second channel setting means for setting the initially-used channel predetermined according to the identification code and for controlling the second channel changing means in response to a user'"'"'s operation in such a manner to freely change the communication channel currently being used by the slave unit, wherein the master unit transmits and receives a signal through the predetermined initially-used-channel indicated by the information stored in the second storage means when the power source connected thereto is turned on, wherein, in case the master unit does not normally reply to the slave unit when the second transmitting means of the slave unit transmits a signal to the master unit, the second channel changing means reads the information representing the initially-used-channel from the fourth storage means and changes the communication channel currently being used by the slave channel according to the information read from the fourth storage means into the initially-used-channel and the second transmitting means of the slave unit transmits a signal again to the master unit through the initially-used-channel, wherein in case the master unit replies to the signal transmitted again from the second transmitting means, the slave unit transmits to the master unit a signal directing the first channel changing means to change the communication channel used by the master unit into the usually-used-channel according to the information representing the usually-used-channel stored in the first storage means.

3. A cordless telephone having a master unit driven by an external power source and a slave unit driven by a battery and using a plurality of communication channels for communication between the master unit and the slave unit and employing an identification code indicating that the master unit and the slave unit are coupled with each other, said identification code being stored in a first and second channel setting means, the master unit having first transmitting means for transmitting data, first receiving means for receiving data, first channel changing means for changing a communication channel currently being used by the master unit, first storage means for storing information representing a usually-used-channel, first channel setting means for setting information representing an initially-used-channel predetermined correspondingly to the identification code in the first channel setting means when the power source connected to the master unit is turned on, second storage means for storing the information representing the initially-used-channel set in the first channel setting means and first control means for controlling the first channel changing means in response to a user'"'"'s operation in such a manner to change the communication channel currently being used by the master unit, the slave unit having second transmitting means for transmitting data, second receiving means for receiving data, second channel changing means for changing a communication channel currently being used by the slave unit, third storage means for storing the information representing the usually-used-channel, second channel setting means for setting information representing initially-used-channel predetermined correspondingly to the identification code in the second channel setting means, fourth storage means for storing the information representing the initially-used-channel set in the second channel setting means and second control means for controlling the second channel changing means in response to a user'"'"'s operation in such a manner to change the communication channel currently being used by the slave unit, wherein the master unit transmits and receives a signal through the initially-used-channel indicated by the information stored in the second storage means when the power source connected thereto is turned on, wherein in case the master unit does not normally send back first confirmation data representing the communication channel currently being used by the master unit and the identification code to the slave unit when the second transmitting means of the slave unit transmits second confirmation data representing the communication channel currently being used by the slave unit and the identification code to the master unit, the second control means causes the second channel changing means to read the information representing the initially-used-channel from the fourth storage means and change the communication channel currently being used by the slave channel according to information read from the fourth storage means into the initially-used-channel and thereafter the second transmitting means of the slave unit transmits the second confirmation data, which represents the changed communication channel currently being used by the slave unit and the identification code, again to the master unit through the initially-used-channel, wherein in case the master unit sends back the first confirmation data in response to the second confirmation data transmitted again from the second transmitting means, the slave unit transmits to the master unit a signal directing the first channel changing means to change the communication channel currently being used by the master unit into the usually-used-channel according to the information representing the usually-used-channel stored in the first storage means.

4. A cordless telephone having a master unit and a slave unit and using a plurality of communication channels for communication between the master unit and the slave unit and employing an identification code indicating that the master unit and the slave unit are coupled with each other, the master unit having first channel setting means responsive to a user'"'"'s operation for freely changing a communication channel currently being used by the master unit, the slave unit having second channel setting means responsive to a user'"'"'s operation for freely changing a communication channel currently being used by the slave unit, wherein the master unit transmits and receives a signal through an initially-used-channel determined from the identification code, wherein in case the master unit does not normally reply to the slave unit when the slave unit transmits a signal to the master unit, the slave unit changes the communication channel currently being used by the slave channel into the initially-used-channel and then transmits a signal again to the master unit through the initially-used-channel.

5. The cordless telephone according to claim 4, wherein the slave unit further comprises storage means for storing information representing the initially-used-channel determined from the identification code, wherein, in case the master unit does not normally reply to the slave unit when the slave unit transmits a signal to the master unit, the slave unit reads the information representing the initially-used-channel from the storage means and changes the communication channel currently being used by the slave channel into the initially-used-channel according to the read information and then transmits a signal again to the master unit through the initially-used-channel.