referring first to fig1 , there is shown a principle of a data transmission system using a human body as a signal transmission path . the system includes a wearable transmitter 10 adapted to be worn on the human body , and a receiver 40 adapted to be connected to an equipment such as a personal computer 60 which utilizes data transmitted from the transmitter for controlled operation of the computer 60 , for example , a verified log - in of the user . the transmitter 10 is connected to a ground electrode 31 and a signal electrode 32 which are integrated into a garment 30 worn by a user in close proximity to the skin of the user . when the user carrying the transmitter 10 touches a touch electrode 41 of the receiver 40 , a signal path is established which extends from the signal electrode 32 through a portion of the user &# 39 ; s body , the touch electrode 41 , an internal circuit of the receiver 40 , a circuit ground 49 of the receiver 40 , the ground g , the other portion of the user &# 39 ; s body , the ground electrode 31 and an internal circuit of the transmitter 10 . the signal path extending through the human body is indicated by dotted lines . thus , a voltage signal applied across the electrodes 31 and 32 is transmitted to the receiver 40 when the user touches the touch electrode 41 . in fig1 , the circuit ground of the receiver 40 is connected to the ground g through a ground line 64 common to the computer 60 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 fig2 , the transmitter 10 includes an electric circuitry and a battery 12 which are accommodated within a case 11 . the circuitry includes a data memory 13 storing data to be transmitted , a controller 14 , a modulator 15 modulating the data into a modulated voltage signal , a signal transmitter 16 applying the modulated voltage signal across the signal electrode 32 and the ground electrode 31 on the garment 30 . also included in the circuitry is a signal detector 20 which is connected to detect a start signal transmitted from the receiver 40 through the signal electrode 32 . the start signal is received across the signal electrode 32 and a circuit ground 19 . the circuit ground 19 may be connected to the ground electrode 31 . only the controller 14 and the signal detector 20 are constantly energized by the battery 12 to be ready for detecting the start signal from the receiver 40 . in the non - operative condition where the transmitter 10 is not transmitting the data , the controller 14 is kept in a sleep mode of consuming less electric current from the battery 12 . when the start signal is received as a consequence of the user touching the touch electrode 41 , the signal detector 20 wakes up the controller 14 which in turn energizes the data memory 13 , the modulator 15 , and the signal transmitter 16 to apply the modulated voltage signal across the signal electrode 32 and the ground electrode 31 for initiating the data transmission . the controller 14 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 14 responds to deenergize the modulator 15 , the signal transmitter 16 and the data memory 13 . for this purpose , the controller 14 includes power switches 21 and 22 which are actuated by the signal detector 20 and the timer to selectively energize and deenergize the modulator 15 , the signal transmitter 16 and the data memory 13 . dotted lines in fig2 show power supply lines from the battery 12 . thus , after transmitting the data , the controller 14 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 transmitter 10 optionally includes a display 24 for visual indication of the data stored in the data memory 15 . as shown in fig3 , the receiver 40 includes various circuits connected to the touch electrode 41 on the exterior of a housing of the receiver . the circuits are energized by a power source 61 provided in the computer 60 to which the receiver 40 is attached . the circuits are commonly connected to a circuit ground 49 which is in turn connected to a ground terminal 69 of the computer for connection with the ground . the circuits include a touch sensor 42 which is connected to the touch electrode 41 to give a touch signal when the touch electrode 41 is touched by the user &# 39 ; s body . also included in the circuits are a start signal generator 43 , a signal detector 44 , a demodulator 45 , and a controller 46 which controls the operations of the circuits . the signal transmitter 43 applies the start signal to the touch electrode 41 in response to the touch signal . the signal detector 44 detects the modulated voltage signal which is transmitted from the transmitter 10 and received across the touch electrode 41 and the circuit ground 49 . the modulated voltage signal thus detected is demodulated at the demodulator 45 to derive the first data which is then fed to the computer 60 to be processed thereat . for example , the first data includes a user &# 39 ; s identification code which is verified at a processor 62 of the computer with reference to various codes assigned to different users and stored in a data memory 63 . when the user &# 39 ; s id is verified as a correct one , the computer completes the log - in sequence to permit the access by the user . under the non - operating condition where the touch electrode 41 is not touched by the human body , only the controller 46 and the touch sensor 42 are energized to be ready for detection of the touching . upon the touch electrode 41 being touched , the touch sensor 42 gives the touch signal to the controller 46 which responds to close switches 51 and 52 to energize the signal transmitter 43 , the signal detector 44 , and the demodulator 45 , thereby generating the start signal and making the circuits ready for receiving the data from the transmitter 10 . the controller 46 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 46 responds to open the switches 51 and 52 , deenergizing the signal transmitter 43 , the signal detector 44 , and the demodulator 45 . thus , the receiver 40 is kept in a sleep mode of consuming less electricity until the touch electrode 41 is touched . dotted lines in fig3 show power supply lines . the receiver 40 further includes an interface 54 in the form of the usb for transferring the data to the computer 60 as well as for receiving the power from a power supply 61 . further , the transmitter 10 and the receiver 40 are designed to effect a bilateral data transmission therebetween . for this purpose , the transmitter 10 additionally includes a demodulator 25 for demodulating data transmitted from the receiver 40 and that the receiver 40 additionally includes a modulator 47 for modulating the data to be transmitted from the receiver 40 . the modulator 47 of gives a modulated voltage signal indicative of the data to be transmitted to the transmitter 10 . the signal transmitter 43 of the receiver 40 is responsible for applying the modulated voltage signal to the touch electrode 41 for data transmission back to the transmitter 10 . in operation , when the user touches the touch electrode 41 of the receiver 40 , the touch sensor 42 provides a touch signal in response to which the controller 46 energizes the modulator 47 , the signal transmitter 43 , the demodulator 45 , and the signal detector 44 . at first , the controller 46 retrieves the data from the data memory 63 of the computer 60 and instructs to give and apply the modulated voltage signal indicative of the data . in response to the voltage signal from the receiver 40 , the controller 14 of the transmitter 10 activates the data memory 13 and performs a suitable processing of the data from the data memory 13 in consideration of the data received from the receiver 40 . the controller 14 updates the data of the data memory 13 depending upon the result of the processing . thereafter , the controller 14 activates the modulator 15 and the signal transmitter 16 so as to transmit the modulated voltage signal indicative of the updated data to the receiver 40 through the electrodes 31 and 32 . the modulated voltage signal received at the receiver 40 is converted into the data which is utilized by the controller 46 for a controlled operation of the computer or passed to another equipment to be processed thereat for a specific operation of the equipment . in this manner , the two - way data transmission is made between the transmitter and the receiver 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 transmitter and the receiver repeats twice or more . in such case , the data in the data memory 13 of the transmitter 10 is modified or updated by the data transmitted from the receiver 40 . also , for minimizing energy consumption , the transmitter 10 is kept in the sleep mode until the modulated voltage signal is received from the receiver 40 , and comes back again in the sleep mode after the data transmission between the transmitter and the receiver is completed . in other words , the data memory 13 , the modulator 15 , the signal transmitter 16 , and the demodulator 21 are energized by closure of the switches 21 and 22 only for a predetermined time period starting from receiving the modulated voltage signal from the receiver . it is within the predetermined time period that the data transmission between the transmitter and the receiver is completed . likewise , the receiver is kept in the sleep mode until the touch electrode 41 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 43 , the modulator 47 , the signal detector 44 , and the demodulator 45 are energized by closure of switches 51 and 52 only for a predetermined time period starting from the touch electrode being touched . as shown in fig1 , and 5 , the garment 30 to which the electrodes 31 and 32 are attached is selected , for example , as a white gown that is always worn by a particular user like a physician , nurse , and laboratory worker while engaging a job requiring a verification of the user . as a matter of course , the garment 30 is not limited to the white gown and may take various types of the clothes such as a uniform for an office , factory , school , and the like organization or group . each of the ground electrode 31 and the signal electrode 32 is in the form of a fabric made by electrically conductive threads and is sewed on the inner surface of the garment 30 with the signal electrode 32 disposed at the shoulders of the garment 30 and with the ground electrode 31 disposed around the lower part of the garment corresponding to a hip and buttocks of the user , as shown in fig4 and 5 . instead of being lined on the garment , the electrodes may be woven into the garment as indispensable parts thereof . the above selected location of the electrodes 31 and 32 is particularly effective when the user access the computer 60 while sitting on a chair as shown in fig6 . in this condition , the ground electrode 31 receives a counter force from the seat of the chair to be pressed against the buttocks of the user , while the signal electrode 32 is pressed against the shoulders of the user with the help of weight of the garment for reliable electrical connection of the electrodes to the human body . it is noted in this connection that the ground electrode 31 is located closer to the foot of the user than the signal electrode 32 along the signal path extending through the human body so that the path extending from the signal electrode 32 toward the finger of the user can be substantially free from , i . e ., cannot be substantially interfered with the path extending from the ground electrode 31 to the foot of the user for reliable signal transmission between the transmitter 10 and the receiver 40 . as shown in fig7 , the case 11 of the transmitter 10 is formed into a nameplate which is made water - tight and accommodates therein the electric circuitry 28 forming the various functional circuits and elements as shown in fig2 , and the battery 12 energizing the circuits . the case 11 is provided with a spring - loaded clip 70 so as to be detachable to the garment , for example , at a breast pocket . the clip 70 is pivotally supported at its one end to the case so as to be movable between a pinching position and a release position . the clip 70 includes a pair of conductive terminals 71 and 72 which are connected to the electric circuitry , i . e ., across the signal transmitter 16 and which are isolated by a dielectric strip 73 . as shown in fig8 and 9 , when the case 11 is attached to the garment , i . e ., the breast pocket , the terminals 71 and 72 come into engagement respectively with pads 35 and 36 provided at one ends of respective leads 33 and 34 extending from the individual electrodes 31 and 32 . thus , the electric circuitry of the transmitter is connected to electrodes . in this connection , the leads 33 and 34 are also made of electrically conductive threads , more particularly , strands of the conductive threads sewed on or into the garment 30 . fig1 to 12 show another preferred embodiment of the present invention in which a case 11 a of the transmitter 10 a is detachable to a sleeve of the garment 30 by means of snap buttons which are normally utilized in association with clothing . that is , the snap button is made of conductive material and composed of a socket 81 and a ball 82 . in this connection , a ground electrode 31 a and a signal electrode 32 a are provided at the sleeve of the garment 30 for direct coupling with the electric circuitry of the transmitter 10 a . other structures are identical to the above embodiment and therefore no duplicated explanation is made herein . the case 11 a is in the form of a water - tight thin plate accommodating the electric circuitry 28 a of the transmitter 10 a and the battery 12 a . the case 11 a is provided with a pair of the sockets 81 which are internally connected to the electrical circuitry of the transmitter 10 a , while the electrodes 31 a and 32 a are provided respectively with the balls 82 . as in the previous embodiment , each electrode is made of conductive threads woven and sewed on or into the sleeve to form an annular band surrounding the sleeve in close proximity to the skin of the user wearing the garment for establishing a reliable electrical connection to the human body . in this embodiment , the balls 82 are sewed directly on the electrodes by use of the conductive threads or press - fitted into the electrode , thereby eliminating the leads extending otherwise by a certain distance along the garment from the electrodes . alternatively , the balls may be provided on the case , or a mixed pair of the ball and socket is provide on the case . in the illustrated embodiments , the ground and signal electrodes 31 and 32 are explained to be formed by the electrically conductive threads , however , the each electrode may be formed as a metal plating deposited on the surface of the garment or deposited on a fabric which is sewed on the garment . also , it is noted that the garment into which the electrodes are integrated is not limited to the garment like the white gown and may be any other kinds of the clothing that is constantly worn by the user who is in access to the verified system . therefore , the clothing may include an armband and wristband integrating the electrodes to which the case of the transmitter can be made electrically and physically detachable by - use of the above described snap buttons . further , the illustrated embodiments show only one application where both of the electrodes are kept in close facing relation with the skin of the user so that both of the electrodes are in direct electrical connection to the user &# 39 ; s body , however , it is equally possible that one of the electrodes is in direct facing relation , i . e ., electrical connection to the user &# 39 ; s body , while the other of the electrodes is arranged to face away from the user &# 39 ; s skin for capacitive connection to the receiver through the air . still further , although the illustrated embodiment is arranged to verify the data , i . e ., the user &# 39 ; s id at the computer 60 , the receiver 40 may be arranged to equip the processor and the data memory so as to have a function of verifying the data from the transmitter , and providing a verified output to an associated device for permitting the access or a required control of the device , for example , permitting an entry of the user into a restricted area .
a data transmission system using a human body as a signal transmission path includes a transmitter and a receiver . the transmitter uses a pair of electrodes which are held in close proximity to the skin of the human body . the transmitter transmits data to the receiver through the signal transmission path partly extending through the human body when a user carrying the transmitter touches a touch electrode of the receiver . the electrodes are integrated into a garment worn by the user in such a manner that the electrodes are kept in a closely facing relation to the skin of the user , thereby establishing the electrical path extending through the human body . with the integration of the two electrodes into the garment , the user wearing the garment as an everyday clothes or uniform can be easy and convenient to carry the transmitter for successful transmission of the data .