Abstract:
The invention discloses a method of transferring calls from a first station of a first telecommunications network (PSTN) including integrated call transfer means to a mobile station connected to a radio communications network. An auxiliary device is intended to automatically trigger a call transfer activation and/or deactivation control by transmitting predefined messages from the auxiliary device which have integrated network transfer means (PSTN) for their destination. The auxiliary device may advantageously be used in a charger of a mobile station and thus it includes detection means for detecting the presence of the mobile station for automatically triggering a call transfer when the station does not rest on its charger.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method of transferring calls from a first station of a first telecommunications network comprising integrated call transfer means to a second station, while an auxiliary device automatically triggers an activation and/or deactivation control for said call transfer. 
     The invention also relates to a device intended to carry out call transfers from a station of a telecommunications network comprising integrated call transfer means to a mobile station of a radio communications network. 
     The invention is advantageously applied to call transfers effected between a fixed station of the conventional public switched network and a mobile station connected to a radio telecommunications network. 
     BACKGROUND OF THE INVENTION 
     Such a method and device for call transfer are known notably from European patent application no. 0 639 034 A1. This document describes a method and a device for transferring calls from a mobile station of a radio communications network to another station. The call transfer is effected via the mobile station which communicates with the network by radio for this purpose. Call transfer instructions are then transmitted from the mobile station to call transfer means integrated with said radio communications network. 
     This method thus makes it necessary that all the incoming calls are intended for the mobile station which then automatically switches them to another station via the integrated transfer means of the radio communications network if the conditions for triggering a call transfer are satisfied. 
     This method, however, has a major drawback when the communication rates to a number of a mobile station are roughly higher than those intended for a fixed station number (which is currently the case). More particularly, in the case where an occasional use of a mobile station is provided, it is more advantageous for the calls to be systematically received by the fixed station and then transferred to the mobile station as required. 
     Indeed, according to the method described in cited document, the calling party always pays the price of a communication to a mobile station whatever the final receiving station. This may be detrimental in the case of calls of clients to a service provider who has a very competitive activity. The kind of example where this method is not satisfactory is that of a client choosing haphazardly a car service in his town in a telephone directory. The numbers of mobile stations being special numbers, the client will have a tendency of calling first a number of a fixed station. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to remedy this detrimental effect by providing a method and a device for call transfer which reduces the overcharge of the communications to a mobile station for the calling party. With this object, only the call number of the station to which a call costs the least is communicated to the calling parties. The call transfers are then automatically effected from this station to the mobile station to which the user can be connected and the cost of the communication from the first station to the mobile station is then billed to the called party. 
     The invention further provides to use call transfer means existing in a telecommunications network to which a station called fixed station whose incoming communications are not expensive is connected and to control these call transfer means by remote control in a manner transparent to the calling party via an auxiliary electronic device connected to this network. 
     For this purpose, a method of the type mentioned in the opening paragraph is characterized in that said control is triggered by the transmission of predefined messages from said auxiliary device which have said integrated transfer means for their destination. 
     According to an important characteristic feature of the invention, a method of the type described above is characterized in that it comprises a detection step for detecting the presence of said mobile radio station by said auxiliary device for triggering said control. Thus, when the mobile station is detected, the calls are normally received by the fixed station. If not, they are automatically transferred from the fixed station to the mobile station at the expense of the called party. 
     The invention also provides an auxiliary device as mentioned in the opening paragraph, characterized in that it comprises means for transmitting call transfer activation and/or deactivation messages to said integrated transfer means and means for keeping said messages in the memory. 
     Preferably, this device is integrated with a battery charger intended to receive a mobile station. 
     These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIGS. 1A and 1B illustrate two different situations in which a method is implemented according to the invention. 
     FIG. 2 illustrates an embodiment of the method according to the invention. 
     FIG. 3 represents an embodiment of the call transfer device according to the invention. 
     FIG. 4 represents a block diagram of an auxiliary device according to the invention. 
     In these Figures, like elements carry like references. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1A and 1B, a fixed station  10  is connected to the Public Switched Telephone Network PSTN and is given a call number Y on this network. A mobile station (or radio telephone)  12  functioning on rechargeable batteries is connected to a mobile radio communications network  14 , for example, according to the GSM standard (Global System for Mobile communications). Its call number is denoted X. A recharging (or charging) device  16  intended to receive the telephone  12  for recharging its batteries is also connected to the PSTN network. According to a variant of the embodiment of the invention, the station  10  and the charger  16  may be connected to the same telephone line. 
     According to the principle of the invention, the user, for example, a car mechanic, desires that the communications received on his radio telephone are billed to him. Thus, he only informs his interested parties of the number Y of his fixed station. Thanks to the call transfer method according to the invention, the communications received by his fixed station while he is moving around with his radio telephone are transferred to the call number X of the radio telephone. 
     In the first situation illustrated in FIG. 1A, it is supposed that the user is carrying out a car repair outside and has taken along his radio telephone in order to be connected. The charger has then detected the absence of the radio telephone and has thus activated the call transfer to the number X. 
     In the second situation illustrated in B in FIG. 1, the user is in the premises and his radio telephone is placed on its charger. This charger has detected its presence and has thus deactivated the call transfer. 
     FIG. 2 illustrates an embodiment of the method according to the invention. In box K 1  (ON) the charger is switched on. Adapter means permit of the detection of the presence of the mobile station MS on the charger  16 . These means will be described in detail in FIGS. 3 and 4. A first test of detecting the presence of the radio telephone is carried out in box K 2 . 
     If the result of this test is negative, the method is proceeded with box K 3  in that a call transfer is triggered. An activation message is then sent to the call transfer means existing inside the network PSTN. According to the preferred embodiment of the invention, this message consists of a DTMF sequence (Dual Tone Multifrequency) transmitted from the charger over the PSTN network. This sequence contains the digital information signals necessary for activating a transfer in accordance with the procedure required by the PSTN network and also an information signal containing a call number X of the radio telephone to which the communications are to be transferred. This sequence is first stored in a memory in the charger and is then transmitted over the PSTN network upon the activation instruction of the charger which charger is triggered by the fact that the absence of the mobile telephone  12  on its charger is detected. 
     Once the transfer has been effected, the method proceeds to box K 4  where the detection means of the charger periodically or continuously test the presence of the mobile station. The method remains in this state as long as the presence of the mobile station has not been detected. The detection of the presence of the mobile station thus puts the method in the state represented in box K 5 . 
     If the result of the first test K 2  is positive, the method carries on with box K 5  with the deactivation of the call transfer. A deactivation sequence DTMF is sent by means of a call transfer of the PSTN network in accordance with the procedure required by the PSTN network. Then a new test for detecting the presence of the mobile station is carried out in box K 6 . The method remains in this state as long as the absence of the mobile station has not been detected. If the charger in effect detects the absence of the mobile station, box K 3  is proceeded to where the call transfer is activated. 
     In a variant of an embodiment of the method according to the invention, while each call transfer activation or deactivation occurs (in the respective states K 3  and K 5 ) after a detection of the absence or presence of the mobile station, this call transfer activation or deactivation is not triggered until after a certain period of time which comprises the counting down of a time delay followed by a confirmation of this detection. The role of this time delay is to avoid detection errors and release an instruction each time the radio telephone is disconnected from its charger for a brief period of time. 
     FIG. 3 shows how the charger  16  is connected to the PSTN network via a standardized connector  32  and a terminal  33  and how it is connected to a supply source by a male plug  34  and a female plug  35 . 
     A male charge connector  36  comprising various pins is intended to co-operate with a female charge connector of the radio telephone to form a recharging loop and thus transmit the charge current from the charger to the batteries of the radio telephone. According to the preferred embodiment of the invention, the connector  36  also includes means for detecting the presence of the radio telephone on the charger. These means will be described with reference to FIG.  4 . 
     For using the device  16  only for its function of charger, it is sufficient to disconnect the connector  32  from the terminal  33 . 
     FIG. 4 illustrates the operation of the charger  16  according to the invention. A 4-bits microcontroller (μC)  43  manages the exchanges of data between the connector  36 , a memory of the EEPROM type  44  and a DTMF frequency generator  46 . 
     The connector  36  detects the presence of the radio telephone via a conventional method called looping back. The connector  36  comprises a pin  47  whose voltage may assume two different values as a function of the presence or absence of the radio telephone. The reading of this voltage by the microcontroller  43  thus permits to detect the presence of the radio telephone on the charger. 
     Memory  44  is intended to store the digital DTMF call transfer sequences (varying with the networks of which one wishes to use the integrated call transfer means) and the call number of the station to which the transfer is to be effected. The programming of the EEPROM  44  may be realized at any moment and in simple manner by the known means. 
     The generator  46  permits to send the DTMF frequencies through the PSTN network via the line interface  48 . A converter  49  is used for converting the AC current into DC current to feed the various components of the charger  16 . 
     When the radio telephone  12  does not rest on the charger  16 , the recharging loop is open and the voltage read on the pin  47  by the microcontroller  43  indicates the absence of the radio telephone. A time delay is then activated. If the voltage read on the pin  47  does not vary significantly before this time delay has expired, the microcontroller  43  will recognize the absence of the radio telephone and will read from the EEPROM  44  the sequence that corresponds to an activation of a call transfer for sending this sequence to the DTMF generator  46 . This generator then sends the sequence over the network via the line interface  48 . 
     When the radio telephone  12  rests on its charger  16 , the recharging loop is closed and the voltage read by the microcontroller  43  on the pin  47  indicates the presence of the radio telephone. If this voltage does not vary before a time delay has elapsed, the microcontroller  43  will read from the EEPROM  44  the sequence that corresponds to a deactivation of a call transfer for sending this sequence to the DTMF generator  46  and after that to the PSTN network. 
     In another embodiment called “manual” embodiment of the invention, an activation or deactivation of a call transfer may be triggered by a manual control from an auxiliary device. This device then has the same characteristic features as the device represented with respect to FIG. 4 except that the charge connector  36  is substituted by an interface element which has, for example, a call transfer button intended to be activated by the user. The activation of this transfer control is then detected by the microcontroller  43  to effect or cancel a call transfer like in the embodiment called “automatic” described previously. 
     This “manual” embodiment is advantageous in the case where the user only wants call transfers to be systematically carried out when he uses his radio telephone away from the charger. In effect, according to the mode of operation of the invention, all the call transfers received on his radio telephone are billed to him. Such an embodiment called “manual” then brings the user more flexibility in the management of call transfers than the previously called “automatic” mode. 
     The invention obviously applies to other network systems than those illustrated in the Figures and is not restricted to the embodiments that have just been described and represented. Other variants of the invention will be clear to a person of ordinary skill in the art, more particularly, by substitution of equivalent technical means, and these variants do not go beyond the scope of the invention.