Abstract:
A radio communicating apparatus for communicating via a radio signal comprises: a connecting unit to connect a terminal and a communication channel; and a controller for controlling the connecting unit so as to disconnect the communication channel when a control signal indicating that the communication is being executed is not received at a predetermined timing.

Description:
This is a continuation of co-pending application Ser. No. 08/378,967, filed on Jan. 26, 1995. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a radio communicating apparatus for performing a communication via a radio signal. 
     2. Related Background Art 
     A master telephone of a conventional cordless telephone changes from a speech communication state to an on-hook state in the case where the master telephone receives an on-hook signal from a slave telephone or cannot detect a carrier from the slave telephone. 
     However, when a power source of an apparatus which generates a radio wave of a speech communication channel used at present for a speech communication or the like is turned on during the speech communication, since the master telephone detects the carrier of the speech communication channel, when the reception of an off-hook signal from the slave telephone fails, the master telephone is not disconnected while capturing the line. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to make it possible to certainly detect that a communication terminal has finished a communication. 
     Another object of the invention is to prevent that a line is erroneously continuously held. 
     Still another object of the invention is to make it possible to properly restart a communication in the case where a state of a communication channel deteriorates after the start of the communication. 
    
    
     The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a structure of a telephone switching apparatus; 
     FIG. 2 is a block diagram of a cordless telephone master; 
     FIG. 3 is a flowchart showing the first control of a control circuit of the telephone switching apparatus embodying the invention; 
     FIG. 4 is a flowchart showing the first control of a control circuit of a cordless telephone master embodying the invention; 
     FIG. 5 is a flowchart showing the second control of the control circuit of the telephone switching apparatus embodying the invention; and 
     FIG. 6 is a flowchart showing the second control of the control circuit of the cordless telephone master embodying the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The first embodiment of the invention will now be described hereinbelow with reference to the drawings. 
     FIG. 1 shows a block diagram of a telephone switching apparatus using the invention. In FIG. 1, a telephone switching apparatus 1 is connected to a digital communication network (ISDN) 11 and an analog communication network (PSTN) 12 through a digital interface 5 and an analog interface 6, respectively. The telephone switching apparatus 1 is also connected to extension exclusive-use telephones 2a and 2b and extension cordless telephones 2c, 2d, and 2e through an extension interface 3. Voice information from each of the above interfaces is switched in a speech communication path 4. A control circuit 7 controls each interface and the speech communication path. A program to execute the control by the control circuit 7 has been stored in an ROM 8. The writing and reading operations of data which is necessary for the control are executed to an RAM 9. 
     FIG. 2 shows a block diagram of a master telephone (also simply referred to as a master) of the cordless telephone. The cordless telephone master is connected to a line from the telephone switching apparatus 1 through an interface 15. The voice information is sent to a tuner 13 through a voice processing circuit 14. Control information is sent to a control circuit 16. A program to control the cordless telephone master has been stored in an ROM 17. The writing and reading operations of data which is necessary for control are executed to an RAM 18. 
     In the above construction, the cordless telephone executes a communication through a plurality of frequency divided communication channels. 
     FIG. 3 is a flowchart showing a control of the control circuit 7 of the telephone switching apparatus using the invention. FIG. 4 is a flowchart showing a control of the control circuit 16 of the master of the cordless telephone using of the invention. Those flowcharts are shown mainly with respect to the portions regarding the invention. 
     First, a method of setting a time interval to monitor a speech communication in the telephone switching apparatus will be described. The time interval for observation of a speech communication is set by numerical values of three digits which are inputted by depressing proper keys for a period of time between a set key and a set key in the extension exclusive-use telephone 2a. That is, in the extension exclusive-use telephone 2a, by depressing the keys such that (set)→(0)→(0)→(0)→(set), a mode such that the speech communication observation is not performed is set. By depressing the keys such that (set)→(0)→(3)→(0)→(set), a mode to execute the speech communication observation every 30 minutes is set. The time interval for the speech communication observation is stored into the RAM 9 of the telephone switching apparatus. 
     Subsequently, the controls in the control circuit 7 of the telephone switching apparatus and the control circuit 16 of the cordless telephone master will now be described with reference to FIGS. 3 and 4. When the cordless telephone enters a speech communication state (S301), the control circuit 7 of the telephone switching apparatus starts a timer to measure the time for speech communication observation (S302). The timer is provided on the RAM 9. When the timer times out (the time set to the time interval for the speech communication observation elapses) in step S303 before the cordless telephone enters the on-hook state in step S305, the control circuit 7 indicates the confirmation of the speech communication to the cordless telephone which is in the speech communication (S304). The timer is restarted. 
     When receiving an indication of the confirmation of the speech communication from the telephone switching apparatus in the speech communication state (S401), the control circuit 16 of the cordless telephone master transmits a speech communication confirmation command (state confirmation command) to a slave telephone (also simply referred to as a slave) (S402). The control circuit 16 starts a timer for waiting for a response to the speech communication confirmation command (S403) and waits for a response from the slave. The timer is provided on the RAM 18. 
     When receiving the speech communication confirmation command, the slave transmits a speech communication confirmation response when it is in the speech communication state. 
     When the response from the slave is received, this means that the speech communication is certainly being executed, so that the control circuit 16 of the master is returned to the ordinary speech communication state (S404). When the timer times out before the response from the slave is received (S405), the control circuit 16 judges that the slave is in the on-hook state, so that the control circuit 16 executes an on-hook process (disconnection of the radio line) and notifies the end of the speech communication state to the control circuit 7 of the telephone switching apparatus 1 (S406). In the speech communication state, in another case where the on-hook signal from the slave is received (S407) or where the carrier of the slave cannot be detected (S408), the control circuit 16 also executes the on-hook process and finishes the speech communication state. 
     When the end of the speech communication state is notified, the control circuit 7 recovers the line. 
     The second embodiment of the invention will now be described hereinbelow with reference to the drawings. 
     FIG. 5 is a flowchart showing the control of the control circuit 7 of the telephone switching apparatus using the invention. FIG. 6 is a flowchart showing the control of the control circuit 16 of the master of the cordless telephone using the invention. Those flowcharts are shown mainly with respect to the invention. 
     The controls in the control circuit 7 of the telephone switching apparatus and the control circuit 16 of the cordless telephone master will now be described hereinbelow with reference to FIGS. 5 and 6. When the time interval for the speech communication observation is set (S501), the control circuit 7 of the telephone switching apparatus notifies the value-of the set time interval to the cordless telephone master (S502). 
     When receiving the speech communication observation time interval from the telephone switching apparatus (S611), the control circuit 16 of the cordless telephone master stores the value of the time interval into the RAM 18 (S612). In the case where keys to register the speech communication observation time interval are provided for the master, the time interval is stored in accordance with an input of such keys. When the telephone enters the speech communication state (S601), the control circuit 16 starts a built-in timer (A) to measure the time interval of the speech communication observation (S602). When the timer (A) times out (S603), the control circuit 16 transmits a speech communication confirmation command (state confirmation command) to the slave (S604) and starts a timer (B) to wait for a response to the speech communication confirmation command (S605) and waits for a response from the slave. 
     When receiving the speech communication confirmation command, the slave transmits the speech communication confirmation response when it is in the speech communication state. When the response from the slave is received, this means that the speech communication is certainly being executed. Therefore, the control circuit 16 restarts the-timer (A) (S602) and is returned to the ordinary speech communication state (S606). 
     When the timer (B) times out before the response from the slave is received (S607), the control circuit 16 executes the on-hook process (disconnection of the radio line) and notifies the end of the speech communication state to the control circuit 7 (S608). In the speech communication state, in another case where the on-hook signal from the slave is received (S609) or where the carrier of the slave cannot be detected (S610), the control circuit 16 also executes the on-hook process and finishes the speech communication state. 
     When the end of the speech communication state is notified, the control circuit 7 recovers the line. 
     In the first and second embodiments, when the speech communication confirmation command is not received at a predetermined interval during the speech communication of the slave, the on-hook process is also executed. 
     In the first and second embodiments, the speech communication confirmation command has been transmitted from the cordless telephone master to the slave. In the third embodiment, however, the speech communication confirmation command is transmitted from the slave to the master at a predetermined interval. When the speech communication confirmation command is not received within a specific time interval on the master side, the on-hook process is performed. 
     The invention is not limited to the cordless telephone connected to an extension of the telephone switching apparatus but can be also applied to a radio terminal connected directly to an external line. 
     Although the present invention has been described above with respect to the preferred embodiments, the invention is not limited to the foregoing embodiments but many modifications and variations are possible within the spirit and scope of the appended claims of the invention.