JPH04249949A - Cordless telephone set - Google Patents

Abstract

PURPOSE:To perform radio connection smoothly by making the execution time of carrier sense into random shape, providing a reception circuit for mobile machine and a reception circuit for fixed station, and deciding the vacancy of a control channel by detection signals from those circuits. CONSTITUTION:A radio control part 24a, when a timing to emit a wave on a control channel being informed from a random timing generating means 25a, detects whetheror not a null channel exists by out-output signals from the reception circuit 28a for fixed station and the reception circuit 27a for mobile machine. The wave on the control channel is emitted only when it is decided that the null channel exists. As a result, it is possible to prevent the waves on the control channel from being emitted simultaneously from plural fixed stations.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless telephone, and more particularly to a cordless telephone equipped with a control channel control device that can smoothly establish a wireless connection between a fixed station and a mobile station.

0002

2. Description of the Related Art A plurality of cordless telephones may be used by being connected to one telephone line. FIG. 5 shows a block diagram when two cordless telephones are connected to one telephone line. Further, FIG. 6 shows a timing chart of the control channel of the cordless telephone. In Figure 5, 1
A and 1b indicate fixed stations of the first and second cordless telephones, and 2a and 2b indicate mobile stations of the first and second cordless telephones. Further, 3 indicates a telephone line.

Now, the low power cordless telephone is
According to the law, carrier sense is required before transmission.

For example, in the cordless telephone shown in FIG. 5, if a call is received on the telephone line 3 at time t0 in FIG. 6, fixed stations 1a and 1b simultaneously perform carrier sense at time t1. Specifically, fixed stations 1a and 1b each check whether mobile stations 2a and 2b are in an idle state, in other words, whether mobile stations 2a and 2b are in a standby state.

As a result of the carrier sense, if the mobile stations 2a and 2b are idle, the fixed stations 1a and 1b
almost simultaneously emits control channel radio waves c1 and d1. In response, the mobile device 2a or 2b responds and outputs a response signal c2 or d2. Thereafter, the mobile terminals 2a and 2b enter a ringing state by switching to a communication channel.

[0006] Since two control channels are assigned to a low-power cordless telephone, the cordless telephone can operate without any problems if up to two are connected to one telephone line.

However, when three or more telephones are connected to one telephone line, for example, in the case of a button telephone or a home telephone, the following problem occurs.

[0008]

[Problems to be Solved by the Invention] For example, as shown in FIG. 7, three cordless telephones are connected to one telephone line, and the radio waves of the control channels of fixed stations 1a and 1c have the same frequency. Assume that the radio wave c1 is.

In the system with the above configuration, as shown in FIG. 8, a call is received via the telephone line 3 at time t0, and fixed stations 1a, 1b, and 1c simultaneously perform carrier sensing at time t1. do. When it is detected by this carrier sense that the mobile stations 2a, 2b, 2c are in an idle state, the fixed stations 1a, 1b, 1c simultaneously emit control channel radio waves c1, d1.

[0010] At this time, since the frequencies of the radio waves c1 emitted by the fixed stations 1a and 1c are the same, the radio waves interfere with each other,
There was a problem that a normal connection could not be established.

Furthermore, as shown in FIG. 9, at time t
Assume that the fixed station 1c receives an extension call at time t2, performs carrier sense, detects that the mobile station 2c is idle, and emits a control channel radio wave c1 at time t3.

However, suppose that an incoming call happens to arrive via the telephone line 3 at time t3, and the fixed station 1a performs carrier sensing. In this carrier sense, fixed station 1a checks whether both mobile stations 2a and 2c are free. Mobile device 2a is naturally vacant, but
Regarding the mobile device 2c, a time t is required after the radio wave c1 of the control channel is emitted from the fixed station 1c until the mobile device 2c outputs a response signal. As a result, the mobile station 2c is also determined to be in an idle state, and at time t4, the fixed station 1a emits a control channel radio wave c1.

[0013] Then, the radio waves emitted from the fixed station 1c starting from time t3 and the radio waves emitted from the fixed station 1a starting from time t4 interfere with each other, and the radio waves emitted from the fixed stations 1c and 1a
In both cases, there was a problem that normal connection to each other's mobile devices could not be established.

[0014] Techniques related to the above-mentioned prior art are disclosed, for example, in JP-A-63-234637 and JP-A-64-82714.

An object of the present invention is to provide a cordless telephone that eliminates the problems of the conventional devices described above and that allows smooth connection between a fixed station and a mobile station when an incoming signal arrives via a telephone line. It is about providing.

[0016]

Means for Solving the Problems In order to achieve the above object, the present invention provides a cordless telephone that wirelessly connects a fixed station and a mobile device, in which the fixed station can control signals emitted by other fixed stations. a receiving circuit for a fixed station that receives a radio wave of the control channel; a receiving circuit for a mobile device that receives a signal responsive to the radio wave of the control channel outputted by each mobile device; Random timing generating means for randomly determining the timing until the radio wave is emitted; and when the random timing generating means is informed of the timing to emit the radio wave of the control channel, The device is characterized in that it is equipped with a wireless control section that detects whether or not a channel is vacant from the output, and instructs a transmitting circuit to emit radio waves of a control channel when the channel is vacant.

[0017]

[Operation] According to the present invention, when the radio control section is informed of the timing for emitting radio waves of the control channel from the random timing generating means, the radio control section outputs the outputs from the fixed station receiving circuit and the mobile device receiving circuit. Detects whether the channel is empty based on the signal, and only when it is determined to be an empty channel,
Emit control channel radio waves.

As a result, control channel radio waves are no longer emitted from a plurality of fixed stations at the same time, and the wireless connection between the fixed station and the mobile device is no longer inhibited by radio wave interference.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing a button telephone device equipped with a cordless telephone according to an embodiment of the present invention. In the figure, 11 is a telephone line, 12 is a main device, 13a, 1
3b and 13c are fixed stations connected to the main device 12, and 14a, 14b and 14c are mobile devices corresponding to the fixed stations 13a, 13b and 13c, respectively.

[0021] In the following explanation, the fixed station 13
a and the mobile device 14a as the first cordless button telephone KT.
1. The fixed station 13b and the mobile device 14b are connected to the second cordless button telephone KT2, and the fixed station 13c and the mobile device 14c are connected to the third cordless button telephone KT2.
It is sometimes called the cordless button telephone KT3.

Next, a specific example of the configuration of the fixed station 13a will be explained with reference to the block diagram of FIG. Note that the fixed stations 13b and 13c also have the same or equivalent configuration as the fixed station 13a, so these configurations are different from those of the fixed station 1.
The explanation of the configuration of 3a shall be used instead.

In FIG. 1, 21a is an extension transmission line connecting the main device 12 and the fixed station 13a, 22a is a communication circuit,
23a is an incoming call detection circuit; 24a is a radio control unit that controls the radio circuit and each peripheral circuit; 25a is the time to start carrier sense; in other words, radio waves of the control channel are emitted from the time when incoming call information is received; This is a random timing generator that randomizes the time until Also, 26
a is a transmitting circuit, 27a is a receiving circuit for a mobile device that receives radio waves from the mobile devices 14a to 14c, that is, response signals and call signals, and 28a is a fixed station other than the mobile device 13b, 1.
A fixed station receiving circuit 29a receives the radio waves from the mobile station receiving circuit 27a and the fixed station receiving circuit 2.
This is an empty channel determining circuit that determines whether the channel being received is in a used state or an empty state from the output signal of the channel 8a.

Next, the fixed stations 13a to 13 having the above-mentioned configurations
The operation of the key telephone device (see FIG. 2) having the function 1 when receiving a call will be explained with reference to the timing chart of FIG.

When an incoming call signal arrives on the telephone line 11 and incoming call information is output from the main device 12, the fixed stations 13a to
Each of the incoming call detection circuits 23a to 23c of 13c detects the incoming call all at once at time t0 shown in FIG. 3, and outputs a detection signal to the respective radio control units 24a to 24c.

[0026] Upon receiving the detection signal, each radio control unit 24a-24c generates a random timing generator 25a-25.
Start monitoring 5c. Random timing generator 25
A to 25c randomly output carrier sense execution times. In FIG. 3, 25a shows the output of the random timing generator of the fixed station 13a, 25b shows the output of the random timing generator of the fixed station 13b, and 25c shows the output of the random timing generator of the fixed station 13a.
The output of the random timing generator of c is shown.

As shown in the figure, at time t1, when the random timing generator 25a of the fixed station 13a of the key telephone KT1 outputs a timing signal, the radio controller 24a outputs a timing signal from the mobile receiver circuit 27a and the fixed station. A control channel setting code is sent to the receiver circuit 28a, and carrier sensing is performed. That is, the wireless control unit 2
4a is a signal from the empty channel determination circuit 29a.
Determine whether the channel is free. Assuming that the signal from the free channel determination circuit 29a indicates that the channel is free, as shown in the figure, the radio control section 24a outputs a transmitting circuit operating signal to operate the transmitting circuit 26a. When the transmitting circuit 26a receives this transmitting circuit operation signal, it transmits a control channel radio wave to the mobile device 14a. From time t2 to time t5 in FIG. 3, the transmitting circuit 26a of the fixed station 13a outputs a radio wave of the control channel, and the mobile device 14a outputs a response signal in response to this. Then, a wireless link is established between the fixed station 13a and the mobile device 14a. Once this wireless line is established, it then shifts to a communication channel and enters a ringing state, so that the idle channel determination circuit 29a of each fixed station determines that it is an idle channel. Now, the time t2~
At times t3 and t4 between t5, when timing signals are output from the corresponding random timing generators 25b and 25c in the fixed stations 13b and 13c of the key telephones KT2 and KT3, respectively, as shown in the figure. The radio control units 24b and 24c perform carrier sense and determine whether the channel is in use or in an idle state based on signals from the idle channel determination circuits 29b and 29c. However, at this time, since the fixed station 13a is using the control channel, the fixed stations 13b and 13c give up on using the control channel.

As a result, the fixed station 1 of the button telephone KT1
The control channel radio waves are now output only from 3a, and there is no interference between the control channel radio waves as in the past.

In the example of FIG. 3, by performing the same operations as described above, a wireless link is established between the fixed station 13c of the key telephone KT3 and the mobile station 14c at time t8,
Mobile device 14c enters a ringing state. Furthermore, time t1
At 0, a wireless link is established between the fixed station 13b of the button telephone KT4 and the mobile station 14b, and the mobile station 14b enters a ringing state.

As a result of the above operations, the key telephone KT
1 to KT3 enter a ringing state at time t11.

Note that in FIG. 3, *1 indicates the case where the control channel was in an idle state during the free channel determination period, and *2 indicates the case where the control channel was in use during the free channel determination period.

FIG. 4 shows a flowchart of the operation of the wireless control section 24a in this embodiment.

[0033] In step S1, it is determined whether or not there is an incoming call, and if this determination is affirmative, the process advances to step S2. In step S2, the random timing generator 25a
Start monitoring. In step S3, it is determined whether or not a timing signal has been input from the random timing generating section 25a, and if this determination is affirmative, the process proceeds to step S4. In step S4, it is determined whether the channel is a vacant channel or not based on a determination signal from the vacant channel determination circuit 29a. When steps S3 and S4 are negative, the process returns to step S2.

If the determination in step S4 is affirmative, the process proceeds to step S5, where a command is given to the transmitter circuit 26a to emit radio waves on the control channel. Subsequently, in step S6, it is determined whether or not a response signal has been received from the mobile device, and if affirmative, the process advances to step S7 to establish a wireless circuit. If it is determined in step S8 that the response signal has not been received even after the predetermined time has elapsed, the process ends.

The present invention is not limited to the above-mentioned button telephone device, but can also be applied to home telephones and the like.

[0036]

[Effects of the Invention] As is clear from the above description, according to the cordless telephone of the present invention, the execution time of carrier sense is randomized, and a receiving circuit for a mobile device and a receiving circuit for a fixed station are provided. Since it is determined whether the control channel is free or in use based on the detection signal, carrier sensing at each fixed station can be performed reliably.

Furthermore, since the emission timings of the control channel radio waves do not overlap, interference of the control channel radio waves can be avoided, and the connection between the mobile device and its corresponding fixed station can be established reliably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a cordless telephone according to an embodiment of the present invention.

FIG. 2 is a system block diagram of a key telephone device that is an embodiment of the present invention.

FIG. 3 is a timing chart for explaining the operation of the embodiment.

FIG. 4 is a flowchart for explaining the operation of the wireless control unit of the embodiment.

FIG. 5 is a block diagram of a conventional device.

FIG. 6 is a timing chart for explaining the operation of the conventional device.

FIG. 7 is another block diagram of the conventional device.

FIG. 8 is a timing chart for explaining the operation of the conventional device.

FIG. 9 is a timing chart for explaining another operation of the conventional device.

[Explanation of symbols]

13a-13c Fixed station 14a-14b Mobile device 23a Incoming call detection circuit 24a Wireless control unit 25a Random timing generator 26a Transmission circuit 27a Mobile device receiving circuit 28a Fixed station receiving circuit 29a Empty channel determination circuit

Claims (1)

[Claims] 1. A cordless telephone that wirelessly connects a fixed station and a mobile station, wherein the fixed station includes a fixed station receiving circuit for receiving control channel radio waves emitted by other fixed stations; a receiving circuit for a mobile device that receives a signal in response to the radio wave of the control channel output by the mobile device; and a random timing generating means that randomly determines the timing from when the incoming signal is received until the radio wave of the control channel is emitted. Then, when the random timing generating means is notified of the timing to emit the radio waves of the control channel, it is detected from the outputs of the fixed station receiving circuit and the mobile device receiving circuit whether or not the channel is free, and when the channel is free, transmitting. 1. A cordless telephone comprising: a wireless control section that instructs a circuit to emit radio waves of a control channel.