Abstract:
Touch-responsive data transmission system for elongating transceiver battery life and assuring one-touch data transmission includes a first transceiver worn on user and a second transceiver connected to equipment utilizing first transceiver data. User contacts first transceiver signal and ground electrodes and touches a second transceiver touch electrode to establish a signal path through user. First transceiver includes a detector for detecting a start signal from the second transceiver signal electrode. Second transceiver includes a generator for generating the start signal upon touching the touch electrode. Receiving the start signal, circuit elements responsible for data transmission are battery-energized to start data transmission from first to second transceivers. Circuit elements responsible for transmitting data remain deenergized until user touches the second transceiver touch electrode to save energy during non-operation and prolong first transceiver battery life. By touching the touch electrode, automatic data transmission remains possible without requiring additional starting procedures.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a data transmission system using a human body as a signal path, and more particularly to a system composed of a first transceiver adapted in use to be worn on a human body and a second transceiver adapted to be connected to an associated equipment which utilize data transmitted from the first transceiver. 
     2. Description of the Prior Art 
     U.S. Pat. No. 4,591,854 discloses a data transmission system using the human body as a signal path. The system includes a portable transmitter in the form of a wrist watch to be worn on a user, and a control unit or signal receiver. The transmitter has a pair of electrodes on the back of the wrist watch for direct contact with the skin of the user. One electrode acts as a signal electrode which is connected through a portion of the user&#39;s body to a touch electrode of the signal receiver, while the other electrode acts as a ground electrode which is coupled through or not through the other portion of the user&#39;s body to a circuit ground of the signal receiver to complete a signal path through the user&#39;s body for data transmission from the wrist watch to the signal receiver. The signal receiver includes a touch sensor to detect touching state and non-touching state of the touch electrode so as to enable the signal receiver to receive the data from the wrist watch when the touching is detected for the purpose of avoiding accidental enabling of equipment connected to the signal receiver by radiated signals. To enable this automatic reception of the data at the signal receiver, the wrist watch has to be always ready for transmitting the data or has to include a manual start switch for starting transmission of data. When the wrist watch is designed to be constantly energized to be always ready for the data transmission, a battery energizing electronic components of the wrist watch is likely to be soon exhausted. When the wrist watch is designed to include the start switch, it adds a cumbersome manual operation, thereby detracting from the touch-responsive data transmission. 
     SUMMARY OF THE INVENTION 
     In view of the insufficiencies, the present invention has been achieved to provide a touch-responsive data transmission system which is capable of elongating the battery life of the transceiver worn on the user&#39;s body yet assuring one-touch data transmission. The system in accordance with the present invention comprises a first transceiver adapted in use to be worn on the user&#39;s body and a second transceiver adapted to be connected to an associated equipment which utilizes data transmitted from the first transceiver. The first transceiver comprises a battery energizing the circuit of the first transceiver, a ground electrode for direct contact with the user&#39;s body to establishing an electrical connection through the user&#39;s body to a ground, and a signal electrode spaced from the ground electrode for direct contact with the user&#39;s body. Also, the first transceiver includes a data memory storing first data to be transmitted, a first modulator which is energized selectively by the battery for converting the first data into a first modulated voltage signal, and a first signal transmitter which is energized selectively by the battery to apply the first modulated voltage signal across the signal electrode and the ground electrode. Further included in the first transceiver are a start signal detector which is constantly energized by the battery for detection of a start signal received through the signal electrode, and a first controller which is constantly energized by the battery and is connected to the start signal detector so as to energize the first modulator and the first transceiver for applying the first modulated signal in response to the start signal. 
     The second transceiver comprises a second circuit ground for connection with the ground, a single touch electrode for direct contact with a portion of the use&#39;s body wearing the first transceiver, a second signal detector connected across the touch electrode and the second circuit ground to detect the first modulated voltage signal, and a second demodulator for converting the first demodulated signal back into the first data. Also, the second transceiver includes a start signal generator which generates the start signal and provides it through the touch electrode, and a touch sensor which is connected to the touch electrode to give a touch signal when the touch electrode is touched by the user&#39;s body. Further included in the second transceiver is a second controller which energizes the start signal generator to provide the start signal upon receiving the touch signal, thereby enabling data transmission from the first transceiver to the second transceiver. Thus, the first signal transmitter and the first modulator of the first transceiver can be kept deenergized until the user touches the touch electrode of the second transceiver, thereby saving energy during non-operated condition and assuring a prolonged battery life of the first transceiver. Also, the transmission of the first data can be made automatically simply by touching the touch electrode and without requiring any additional starting procedure. This is particularly advantageous in a case where the first transceiver is realized in the form of a battery operated wrist watch for use in a keyless entry system for access to a vehicle, restricted equipment, and restricted area. 
     Preferably, the second transceiver further includes a second modulator for converting second data into a second modulated voltage signal which is applied between the touch electrode and the second circuit ground for bilateral data transmission between the first and second transceivers. To receive the second data from the second transceiver, the first transceiver includes a first demodulator for converting the second modulated signal, which is detected through the signal electrode, into the second data. Further, the first controller has a function of modifying the first data in accordance with the second data. This arrangement is advantageous when the present system is utilized in an automated gate which permits the entry of a person wearing the first transceiver at a certain charge or fare. Thus, each time the person passes through the gate, the fee determined by the second data is subtracted from a credit stored as the first data of the first transceiver for updating the first data by the second data. 
     It is preferred that that first signal transmitter includes a current regulator which keeps a current flowing between the signal electrode and the ground electrode substantially at a fixed level for the purpose of successfully making reliable data transmission irrespective of differing electrical resistance of differing portions of the skin in contact with the signal and ground electrodes. 
     At least one of the signal electrode, the ground electrode, and the touch electrode may be coated with an insulation layer for making capacitive coupling with the user&#39;s body, avoiding the occurrence of electrical double layer at the interface between the user&#39;s skin and the electrode which would cause electrical polarization, the source of undesired noise. 
     The second circuit ground may be connected to the ground through a ground line for reducing impedance between the second circuit ground and the ground to which the ground electrode is connected through the user&#39;s body. 
     Also, the second transceiver is preferred to have an electrically conductive chassis to which the second circuit ground is connected. 
     Further, the second circuit ground may be connected to an electrically conductive sheet which is adapted to be installed on a site such that the human body wearing the first transceiver stands on the conductive sheet. Thus, it is possible to reduce the impedance between the second circuit ground and the user&#39;s body for reliable data transmission from the first transceiver to the second transceiver through the user&#39;s body. 
     The first transceiver may additionally include a display for indication of the first data so that the user can check the data. The data memory of the first transceiver may be detachable to the first transceiver so that the data memory can be installed on a separate writer for rewriting the first data or can be replaced with another data memory. 
     The first transceiver is held on a disk with the signal electrode and the ground electrode being arranged on one face of the disk. Thus, the first transceiver can be readily incorporated into a wrist watch with the disk forming the back plate of the watch. 
     Alternately, the first transceiver may be held on a ring with the signal electrode and the ground electrode being arranged on an interior face of the ring. Thus, the first transceiver can be easy to be carried on the user as well. 
     The second transceiver may be configured such that the touch sensor and the second controller are constantly energized by a power source to be always read for operation, while the second signal detector and the second demodulator are selectively energized by the power source. The second controller is responsive to the touch signal to energize the second signal detector and the second demodulator. Thus, the second signal detector and the second demodulator are kept deenergized until the second controller receives the touch signal for saving the power while the second transceiver is non-operating condition of not receiving the first data from the first transceiver. 
     In addition, the second controller has a function of deenergizing the second signal detector and the second demodulator after deriving the first data. More preferably, the second controller is configured to provide a predetermined time period for receiving the first demodulated voltage signal and to deenergize the second signal detector and the second demodulator after the elapse of the predetermined time period. 
     These and still other objects and advantageous features of the present invention will become more apparent from the following description of the preferred embodiments when taken in conjunction with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view illustrating a basic concept of a data transmission system in accordance with the present invention; 
     FIG. 2 is a block diagram of a portable transceiver of the above system adapted to be worn on the user&#39;s body; 
     FIG. 3 is a block diagram of an associated transceiver of the above system adapted to be installed to an equipment utilizing the transmitted data; 
     FIG. 4 is a perspective view of the portable transceiver; 
     FIG. 5 is a perspective view of the portable transceiver incorporated in a wrist watch; 
     FIG. 6 is a perspective view of the portable transceiver realized in the form of a ring; 
     FIG. 7 is schematic view of the system utilized for a keyless entry system for a vehicle; 
     FIG. 8 is a block diagram of a portable transceiver utilized in a data transmission system in accordance with another embodiment of the present invention; 
     FIG. 9 is a block diagram of an associated transceiver of the above system; and 
     FIG. 10 is a schematic view of the system utilized in an automated gate system. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring first to FIG. 1, there is shown a principle of a data transmission system using a human body as a signal transmission path. The system includes a portable transceiver  10  (hereinafter referred to as a first transceiver) adapted to be worn on the human body, and an associated transceiver  30  (hereinafter referred to as a second transceiver) adapted to be installed on an equipment  50  which utilizes data transmitted from the first transceiver for controlled operation of the equipment. The first transceiver  10  has a signal electrode  11  and a ground electrode  12  which are held in contact with the user&#39;s body. When the user wearing the first transceiver  10  touches a touch electrode  31  of the second transceiver  30 , a signal path is established which extends from the signal electrode  11  through a portion of the user&#39;s body, the touch electrode  31 , an internal circuit of the second transceiver  30 , a circuit ground of the second transceiver  30 , a ground G, the other portion of the user&#39;s body, the ground electrode  12  and an internal circuit of the first transceiver  10 . The signal path extending through the human body is indicated by dotted lines. Thus, a voltage signal applied across the electrodes  11  and  12  is transmitted to the second transceiver  30  when the user touches the touch electrode  31 . In FIG. 1, the circuit ground of the second transceiver  30  is connected through a ground line  54  to the ground G for the sake of simplicity. However, the circuit ground may be capacitively connected to the ground G or even capacitively connected directly to the major portion of the user&#39;s body for establishing the signal path. 
     As shown in FIG. 2, the first transceiver  10  includes a battery  14  and various circuits energized by the battery. The circuits includes a data memory  15  storing data to be transmitted, a controller  16 , a modulator  17  modulating the data into a modulated voltage signal, a signal transmitter  18  applying the modulated voltage signal across the signal electrode  11  and the ground electrode  12  which are spaced each other by about 5 to 10 mm. Also included in the circuits is a start signal detector  20  which is connected to detect a start signal transmitted from the second transceiver  30  through the signal electrode  11 . The start signal is received across the signal electrode  11  and a circuit ground  19 . The circuit ground  19  may be connected to the ground electrode  12 . Only the controller  16  and the start signal detector  20  are constantly energized by the battery  14  to be ready for detecting the start signal from the second transceiver  30 . In the non-operative condition where the first transceiver  10  is not transmitting the data, the controller  16  is kept in a sleep mode of consuming less electric current from the battery  14 . When the start signal is received as a consequence of the user touching the touch electrode  31 , the start signal detector  20  wakes up the controller  16  which in turn energizes the data memory  15 , the modulator  17 , and the signal transmitter  18  by the battery  14  to apply the modulated voltage signal across the signal electrode  11  and the ground electrode  12  for initiating the data transmission. The controller  16  incorporates a timer which starts upon detection of the start signal to provide a predetermined time during which the data is transmitted. After the elapse of the predetermined time, the controller  16  responds to deenergize the modulator  17 , the signal transmitter  18  and the data memory  15 . For this purpose, the controller  16  includes power switches  21  and  22  which are actuated by the output of the start signal detector  20  and the timer to selectively energize and deenergize the modulator  17 , the signal transmitter  18  and the data memory  15 . Dotted lines in FIG. 2 show power supply lines from the battery. Any other means for determining the end of the data transmission may be utilized instead of the timer. Thus, after transmitting the data, the controller  16  goes back into the sleep mode of consuming less current or energy but being kept ready to detect of the start signal for another data transmission. 
     The signal transmitter  18  is designed to flow substantially constant current between the signal electrode  11  and the ground electrode  12  when applying the modulated voltage signal there across irrespective of varying electrical resistance between the electrodes through a portion of the human body, thereby assuring reliable data transmission to the second transceiver  30 . Further, the first transceiver  10  optionally includes a display  24  for visual indication of the data stored in the data memory  15 . 
     As shown in FIG. 3, the second transceiver  30  includes various circuits connected to the touch electrode  31  disposed outside or on the exterior of a housing of the transceiver. The circuits are energized by a power source  51  provided in the equipment  50  to which the second transceiver  30  is attached. The circuits are commonly connected to a circuit ground  39  which is in turn connected to a ground terminal  59  of the equipment for connection with the ground G. The circuits includes a touch sensor  32  which is connected to the touch electrode  32  to give a touch signal when the touch electrode  31  is touched by the user&#39;s body. Also included in the circuits are a start signal generator  33 , a signal detector  34 , a demodulator  35 , and a controller  36  which controls the operations of the circuits. The start signal generator  33  applies the start signal to the touch electrode  31  in response to the touch signal. The start signal generated is, for example, a uniform AC voltage signal. The signal detector  34  detects the modulated voltage signal which is transmitted from the first transceiver and received across the touch electrode  31  and the circuit ground  39 . The modulated voltage signal thus detected is demodulated at the demodulator  35  to derive the first data which is then fed to the equipment to be processed thereat. 
     Under the non-operating condition where the touch electrode is not touched by the human body, only the controller  36  and the touch sensor  32  are energized to be ready for detection of the touching. Upon the touch electrode  31  being touched, the touch sensor  32  gives the touch signal to the controller  36  which responds to close switches  41  and  42  to energize the start signal generator  33 , the signal detector  34 , and the demodulator  35 , thereby generating the start signal and making the circuits ready for receiving the data from the first transceiver. The controller  36  also includes a timer which starts, upon receiving the touch signal, to provide a predetermined time interval during which the data transmission from the first transceiver  10  is expected to complete. After the elapse of the predetermined time interval, the controller  36  responds to open the switches  41  and  42 , deenergizing the start signal generator  33 , the signal detector  34 , and the demodulator  35 . Thus, the second transceiver  30  is kept in a sleep mode of consuming less electricity until the touch electrode  31  is touched. Dotted lines in FIG. 3 show power supply lines. The second transceiver  30  further includes an interface  44  for transferring the data to the equipment as well as for receiving the power supply therefrom. 
     As shown in FIG. 4, the circuits of the first transceiver  10  are integrated into a single chip  60  which is mounted on a disk  61  together with the button-shaped battery  14 . The signal electrode  11  and the ground electrode  12  are disposed on the back of the disk  61 . The disk  61  is incorporated into a wrist watch as a back plate thereof, as shown in FIG. 5, so that the electrodes  11  and  12  can be always kept in contact with the arm of the user. Alternately, the chip  60  may be incorporated together with the button-shaped battery  14  in a gem-like shell  64  which is supported on top of a ring  65 . The signal electrode  11  and the ground electrode  12  are disposed on the interior of the ring  4  to be always kept in contact with the finger of the user. Likewise, the circuit of the second transceiver  30  may be integrated into a single chip so as to be readily incorporated or attached to the equipment. At least one of the signal electrode  11 , the ground electrode  12 , and the touch electrode  31  may be covered with a dielectric material to establish a capacitive coupling to the corresponding portion of the user&#39;s body, avoiding the electrical double layers at the interface between the electrode and the user&#39;s body for reliable data transmission. 
     It is noted that the circuits of the first and second transceivers are shown according to their functions in FIGS. 2 and 3 for easy understanding of the operations of the transceivers. Therefore, the modulator  17  and the demodulator  35  may be realized by software schemes included in the respective controllers  16  and  36 , rather than by hardware schemes. 
     The second transceiver may include a chassis of electrically conductive material to which the circuit ground is coupled. The chassis has a sufficient surface area for establishing a strong capacitive coupling to the ground G for effective data transmission through the human body between the first and second transceivers. Alternately, the circuit ground of the second transceiver may be directly connected to the ground G by means of a conductive wire or line. Further, in order to enhance the electrostatic coupling between the human body and the circuit ground of the second transceiver, it may be effective to use an electrically conductive sheet which is adapted to be installed on a site such that the human body wearing the first transceiver stands on the conductive sheet. 
     FIG. 7 shows one typical application of the present system for a keyless entry system of a vehicle. The first transceiver  10  in the form of the wrist watch is carried by the user, while the two second transceivers  30  are embedded in a door  80  of the vehicle to be connected commonly to a door lock mechanism  85 . One transceiver  30  is utilized as a door opening sensor with the touch electrode  31  forming a door handle  81 , while the other transceiver  30  is utilized as a door locking sensor with the touch electrode  31  forming a door lock  82 . The circuit grounds of the two transceivers  30  are commonly connected to a body of the vehicle. When the user wearing the first transceiver  10  touches the door handle  81 , the data stored in the data memory of the first transceiver  10  is transmitted to the second transceiver  30  in a manner as described hereinbefore. The data, which is an identification data for the vehicle, is compared with a reference data stored in the door lock mechanism. When the received data is judged to coincide with the reference data, the door lock mechanism  85  operates to unlock the door. When the user touches the door lock  82  on the other hand, the associated transceiver  30  gives the received data to the mechanism  85  which responds to identify the received data and operate to lock the door when the received data is coincide with the reference data. Alternately, the second transceiver may be specifically designed such that the controller  36  stores the reference data and has a function of comparing the received data with the reference data so as to give a unlock signal and a lock signal for actuating the mechanism  85  to unlock and lock the door. 
     Likewise, the present system can be also adapted to an ignition system for starting the vehicle&#39;s engine. For instance, the second transceiver can be embedded in a suitable area around a vehicle&#39;s dashboard with the touch electrode exposed at an easily accessible position. Thus, the user wearing the first transceiver can be easy to start the engine simply by touching the touch electrode. 
     Referring to FIGS. 8 and 9, there is shown a data transmission system in accordance with a second embodiment of the present invention which is designed to effect a bilateral data transmission between a first transceiver  10 A and a second transceiver  30 A. These transceivers are identical to those of the first embodiment except that the first transceiver  10 A further includes a demodulator  25  for demodulating data transmitted from the second transceiver  30 A and that the second transceiver  30 A further includes a modulator  37  for modulating the data to be transmitted from the second transceiver  30 A Like circuit components are designated by like reference numerals with a suffix letter of “A”. The modulator  37  of the second transceiver  30 A gives a modulated voltage signal indicative of the data to be transmitted to the first transceiver  10 A. The signal transmitter  33 A of the second transceiver  30 A is responsible for applying the modulated voltage signal to the touch electrode  31 A for data transmission to the first transceiver. The voltage signal also acts as the start signal for starting the data transmission from the first transceiver  10 A to the second transceiver  30 A. In this sense, the signal transmitter  33 A serves as the start signal generator  33  of the first embodiment. In this connection, the signal detector  20 A of the first transceiver  10 A detects the modulated voltage signal transmitted from the second transceiver  30 A and therefore serves as the start signal detector  20  of the first embodiment. 
     In operation, when the user wearing the first transceiver  10 A touches the touch electrode  31 A of the second transceiver, the touch sensor  32 A provides a touch signal in response to which the controller  36 A energizes the modulator  37 , the signal transmitter  33 A, the demodulator  35 A, and the signal detector  34 A. At first, the controller  36 A retrieves the data from a data memory  52 A of the equipment  50  and instructs to give and apply the modulated voltage signal indicative of the data. In response to the voltage signal from the second transceiver  30 A, the controller  16 A of the first transceiver  10 A activates the data memory  15 A and performs a suitable processing of the data from the data memory  15 A in consideration of the data received from the second transceiver  30 A. The controller  16 A updates the data of the data memory  15 A depending upon the result of the processing. Thereafter, the controller  16 A activates the modulator  17 A and the signal transmitter  18 A so as to transmit the modulated voltage signal indicative of the updated data to the second transceiver  30 A through the electrodes  11 A and  12 A. The modulated voltage signal received at the second transceiver  30 A is converted into the data which is utilized by the controller  36 A for a controlled operation of an equipment or passed to the equipment to be processed thereat for a specific operation of the equipment. In this manner, the two-way data transmission is made between the first and second transceivers in a half-duplex manner. Depending upon a specific application to which the system is applied, the system may be designed to have more than one data transmission cycles in which the one-way data transmission from either of the first and the second transceiver repeats twice or more. In such case, the data in the data memory  15 A of the first transceiver  10 A is modified or updated by the data transmitted from the second transceiver  30 A. 
     Also in this embodiment, the first transceiver  10 A as well as the second transceiver  30 A are designed to be of less energy consumption type. That is, the first transceiver  10 A is kept in the sleep mode of energizing only the controller  16 A and the signal detector  20 A until the modulated voltage signal is received from the second transceiver  30 A, and comes back again in the sleep mode after the data transmission between the first and second transceivers are completed. In other words, the data memory  15 A, the modulator  17 A, the signal transmitter  18 A, and the demodulator  25  are energized by closure of the switches  21 A and  22 A only for a predetermined time period starting from receiving the modulated voltage signal from the second transceiver  30 A. It is within the predetermined time period that the data transmission between the first and second transceivers is completed. Likewise, the second transceiver  30 A is kept in the sleep mode of energizing only the controller  36 A and the touch sensor  32 A until the touch electrode  31 A is touched by the human body, and come back to the sleep mode after the data transmission between the first and second transceivers are completed. Thus, the signal transmitter  33 A, the modulator  37 , the signal detector  34 A, and the demodulator  35 A are energized by closure of switches  41 A and  42 A only for a predetermined time period starting from the touch electrode being touched. Within the predetermined period, the data transmission between the first and second transceivers is completed. Therefore, if a person not wearing the first transceiver touches the touch electrode of the second transceiver, the whole circuits of the first and the second transceivers are energized only for the limited time periods, respectively, for saving the energy. 
     FIG. 10 shows a specific application of the data transmission system of the second embodiment to an automated gate installed on a railway station or the like which charges the person utilizing an associated facility. When the system is applied to the automated gate of the rail way station, the data in the first transceiver  10 A includes information as contained a conventional ticket or pass. The second transceiver  30 A is embedded in a gate  90  and is connected to a power source in the gate. The circuit ground of the second transceiver is connected to an electrically conductive sheet  94  on which the person stands for enhancing the capacitive coupling between the human body and the circuit ground. Alternately, the circuit ground may be simply connected to the ground. As soon as the person wearing the first transceiver  10 A touches the touch electrode  31 A exposed on top of the gate  90 , the data transmission starts between the first and second transceivers and the data received at the second transceiver is processed to see whether the data indicates information which permits the person to pass through the gate. Such data processing is made in the controller of the second transceiver or a gate controller  91  equipped in the gate  90  to receive the data from the second transceiver. If the data shows that the person is permitted to pass through, the gate controller  91  is activated to open a door  92 . In the like manner as in a conventional automated ticket gate, the data on either one of the first and second transceivers can be modified by the data in view of the data on the other transceiver. Thus, the present system enables a ticket-less gate system which is free from using the conventional ticket or pass and is therefore convenient for the user. 
     In this connection, the data of the first transceiver  10 A can be renewed at an expense of corresponding fee with the use of the second transceiver  30 A as a ticket machine. That is, the data of the first transceiver  10 A can be written by data transfer from the second transceiver  30 A. Alternately, the data memory of the first transceiver  10 A can be made detachable so that the data can be renewed with the use of a separate data writer. The data in the data memory is indicated at the display for confirmation by the user. 
     Further, the present system can be well adapted for a cashless transaction though electronic money. In this application, the first transceiver  10 A is adapted to store the electronic money in the data memory, while the second transceiver is installed at a register in a shop or POS (point of sale) terminal. When the user wearing the first transceiver touches the touch electrode of the POS terminal, for example, at the reception of a product or service, the data indicating the charge of the product or the service is transmitted to the data memory of the first transceiver. Subsequently, the data or the electronic money for settlement of the charge is transmitted from the first transceiver to the second transceiver to update the data processed at the POS terminal. At the same time, the electronic money in the first transceiver is subtracted by the charge to update the electronic money which is indicated at the display for confirmation by the user. The electronic money of the first transceiver can be written at a bank or financial institution by the data transmission from the second transceiver installed as a money generating device in exchange of a cash or deposited money. Further, the data memory may be detachable to the first transceiver so as to placed singly in a dedicated money generating device for rewriting the electronic money. The electronic money stored in the first transceiver can be checked at the display of the first transceiver. 
     Further, the present system can be well adapted for a pay phone system in which the second transceiver is installed in a pay phone with the touch electrode exposed on a handset. Thus, when the user wearing the first transceiver grasps the handset, the data transmission between the first and second transceiver can be made for payment of the telephone charges. 
     List of Reference Numerals 
       10  first transceiver 
       11  signal electrode 
       12  ground electrode 
       14  battery 
       15  data memory 
       16  controller 
       17  modulator 
       18  signal transmitter