Abstract:
A method and device are disclosed for detecting successful transfers between a Universal Serial Bus (USB) port and a USB smart card and generating a signal that provides an indication of the USB transaction activity. This USB transaction activity signal is modulated according to the USB transaction activity and drives a Light Emitting Diode (LED) in a preferred embodiment of the invention. A counter internal to the USB smart card scales the transaction activity signal such that it is perceptible to the user. Because the current through the LED depends upon the USB transaction activity, the brightness of the LED varies according to the USB transaction activity. The LED may be driven from a current mirror sink or source, or a current switch sink or source.

Description:
BACKGROUND 
     The invention relates generally to Integrated Circuit (IC) cards or smart cards used in processing transactions involving goods and services. Smart cards are plastic cards having microprocessor and memory circuits attached to the front or back side that connect to electrical contacts located on a front side of the card. The circuits are activated and data accessed from the card by inserting the card into a reader device that makes connections to the electrical contacts. More particularly, the invention relates to a device and method for connecting a smart card having a Universal Serial Bus (USB) interface to smart card reader devices that require no active electronic circuitry. Furthermore, the invention relates to a novel method and device for providing visual indication of data flow activity from the smart card. 
     Smart cards are a class of data cards. Data cards used in processing transactions are either passive or active in nature. Passive data cards include traditional credit, debit and ATM cards that make use of stored data on a magnetic strip on the back of the card. When a transaction is processed using a passive data card, transaction verification is generally required via a reader device connected to a remote computer over a telephone network. During a transaction, data may be written and read from the magnetic strip. Active data cards or smart cards make use of processor and memory circuits embedded on the card that are activated when the card is connected to a reader device. Since smart cards may contain the intelligence required to complete a transaction, the transaction may be completed locally without resorting to a telephone connection to a remote transaction verification facility. In addition to storing data related to the owner&#39;s account such as identification number and account balance, the circuits also contain encryption for security purposes. Smart cards are used in many applications, including Subscriber Identification Module (SIM) in Global System for Mobile (GSM) telephones, TV satellite receivers, banking, health care programs, parking and highway toll payment, etc. Smart cards are expected to find increasingly wider application, eventually replacing magnetic strip type data cards. 
     The basic smart card standard is the International Standard ISO 7816, which provides detailed requirements for the physical, electrical, mechanical, and application programming interface for IC cards with contacts. In particular, International Standard ISO 7816-1 Physical Characteristics, International Standard 7816-2 Dimension and Location of the Contacts, International Standard ISO 7816-3 Electronic Signals and Transmission Protocols, and International Standard ISO 7816-10 Electronic Signals and Answer to Reset for Synchronous Cards are incorporated herein by reference. This standard provides for a serial interface connection to the smart card. In a great majority of cases, these cards are used in a reader connected to a computer. The reader for smart cards that comply with the ISO standard contains electronic circuits that enable communication between the card and the computer. The smart card is inserted into a card reader connector that allows a card reader first interface to communicate with the smart card. A second card reader interface is connected to a computer by means of a serial port link, a parallel port link, or a Universal Serial Bus (USB). The smart card reader based on the ISO standard makes use of a micro-controller with its associated software. Electronic components perform the task of translating signals between the smart card and the computer. Some of these components are dedicated to the visualization of the data flow between the application running on the computer and the smart card. 
     The ISO 7816-3 class B operating conditions make use of the RESET (RST), clock (CLK) and input/output (I/O) communication signals. A smart card reader generates signals RST, CLK and merely buffers the half-duplex communication link on I/O. The signals VCC, GND, RST, CLK and I/O are connected to smart card module contacts. The ISO 7816 smart card reader provides for communication between the computer-based customer application and the smart card by means of an electronic interface circuitry. This interface drives a device that provides a visual indication of I/O activity in the link. Generally, a Light-Emitting Diode (LED) is used for visual indication. 
     The Universal Serial Bus (USB) has recently become firmly established and has gained wide acceptance in the Personal Computer (PC) marketplace. The USB was developed in response to a need for a standard interface that extends the concept of “plug and play” to devices external to a PC, and enables users to install and remove external peripheral devices without having to open the PC case or to remove power from the PC. The USB provides a low-cost, half-duplex serial interface that is easy to use and readily expandable. The USB also supplies up to 500 mA of current at 5 volts to interconnected devices. The USB is currently defined by the Universal Serial Bus Specification written and controlled by USB Implementers Forum, Inc., a non-profit corporation founded by the group of companies that developed the USB Specification. In particular, Chapter 5 USB Data Flow Model, Chapter 7 Electrical, and Chapter 8 Protocol Layer of Universal Serial Bus Specification are incorporated herein by reference. The increasingly widespread use of the USB in computers has led smart card reader manufacturers to develop USB interfaces for connection of their products to computers to complement the existing serial and parallel interfaces. However, because of the differences between the serial interface defined by ISO 7816 and the serial interface defined by the USB specification, smart cards have not been directly compatible with the USB specification. And different card reader configurations have been required due to incompatibility constraints between the various computer interface standards. 
     The widespread use of the USB in computers has led smart card and smart card reader manufacturers to further develop their products and further reduce costs. A USB smart card reader establishes a communication link between a computer-based application and a smart card or plug module. The USB smart card reader or the USB token reader provide contacts for the interconnections between the USB signals and the four corresponding contact zones of a smart card module fitted out with an IC. The USB smart card reader connects smart card module contacts C 1  and C 5  as well as pins C 4  and C 8  respectively to the USB signals V BUS , GND, D+ and D−. There is no electronic circuitry that enables the activity of the link to be reported. The smart card reader complexity has been transferred into the computer, reducing the overall costs. The USB smart card needs a pass-through connector and a driver to communicate with the computer. This architecture reduces the number of electronic components and consequently the cost without compromising the data transfer speed and the transfer reliability. There is only one IC on a USB smart card to perform communications, computing and storage. 
     For the foregoing reasons, there is a need to provide a smart card with a USB interface that enables a smart card to connect to an USB port without the need for any interposing electronic circuitry, enabling application software in a computer to communicate through a specific smart card software driver directly with the USB interface on the smart card. There is a further need to provide a visual indication of successful data transfers between a computer and an IC module positioned on a smart card. 
     SUMMARY 
     The present invention is directed towards a method and device for providing a smart card with the capability of supporting the serial interface defined by the USB specification. It relates to a physical link between a USB port and a smart card. Furthermore, the present invention is also directed towards a method and device for connecting a smart card to a USB port with a simple connector without the need for any interposing electronic circuitry. The invention further relates to a device and method to visualize data flow to and from a smart card. 
     A communication pipe is established between the client software in a computer and USB smart card endpoints. A USB smart card serial engine captures the downstream traffic and delivers it to a smart card micro-controller. The USB smart card serial engine broadcasts the upstream traffic from the smart card micro-controller to the computer. The upstream and the downstream traffic are composed of packets. Every time a packet transfer occurs without error, the USB smart card serial engine hardware generates a Correct TRansfer (CTR) flag that results in an interrupt. The USB smart card software clears this flag once the interrupt has been serviced. The CTR signal drives a first stage of a ten-bit counter. One output is selected for driving an I/O buffer connected to an I/O connector pin. This pin is connected to an LED on a smart card reader that blinks at a pace set by the USB traffic. All functions are included in a single IC, and the only electronic components required in the smart card reader are a LED to provide visual indication of data flow activity, the passthrough connector and in some embodiment a resistor limiting the current in the LED. The present invention provides a method and device that allows USB traffic between a host computer and a USB smart card to be visualized. 
     A method having features of the present invention comprises transmitting and receiving USB packets comprising differential serial signals between the smart card module and the USB port, generating a correct transfer signal by the smart card module upon successful transmission and reception of a USB packet and signaling transaction activity based on the correct transfer signal. The signaling step may include connecting the correct transfer signal to an input of a counter, both positioned within the smart card module, and signaling transaction activity based on an output of the counter. The method may further include selecting an output of the counter so that the user is provided with a perceptible indication of signaling transaction activity. It may also include connecting the output of the counter to an output buffer positioned within the smart card module that drives a LED. The output buffer may comprise a current source circuit connected to a GND reference voltage. The output buffer may comprise a current source circuit connected to a V BUS  supply voltage. The output buffer may comprise a switch circuit connected to a V BUS  supply voltage. The output buffer may comprise a switch circuit connected to a GND reference voltage. 
     Another embodiment of the present invention may comprise transmitting and receiving USB packets comprising differential serial signals between the USB port and external terminals of transceivers positioned within the smart card module, connecting internal terminals of the transceivers to inputs of a serial engine positioned within the smart card module, interconnecting a correct transfer signal from an output of the serial engine to a micro-controller and a counter, both positioned within the smart card module, controlling the counter from the micro-controller, driving an input of an output buffer positioned within the smart card module from an output of the counter, and activating a device from an output of the output buffer for signaling transaction activity based on the correct transfer signal. The device being activated may be a LED, having an anode and a cathode. 
     The method may further include connecting the anode of the LED to a V BUS  supply voltage of the smart card module, connecting the cathode of the LED to an I/O contact of the smart card module, connecting a second NMOS transistor of a current mirror circuit within the smart card module between the I/O contact and a GND reference voltage contact for providing a modulated current sink for illumination of the LED, connecting a first NMOS transistor of the current mirror circuit within the smart card module to the second NMOS transistor, and providing a modulated current to the first NMOS transistor from the output of the output buffer that reflects the USB transaction activity, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The cathode of the LED may be connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
     The method may further include connecting the anode of the LED to an I/O contact of the smart card module, connecting the cathode of the LED to a GND reference voltage of the smart card module, connecting a second PMOS transistor of a current mirror circuit within the smart card module between the I/O contact and a V BUS  Supply voltage contact for providing a modulated current sink for illumination of the LED, connecting a first PMOS transistor of the current mirror circuit within the smart card module to the second PMOS transistor, and providing a modulated current to the first PMOS transistor from the output of the output buffer that reflects the USB transaction activity, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The method may include the anode of the LED being connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
     The method may further include connecting the cathode of the LED to a GND reference voltage of the smart card module, connecting a first terminal of a resistor to the anode of the LED, connecting a second terminal of the resistor to an I/O contact of the smart card module, connecting a PMOS transistor switch of a current switch circuit within the smart card module between the I/O contact and a V BUS  supply voltage contact, and providing a modulated voltage source from the output of the output buffer that reflects the USB transaction activity to a gate terminal of the PMOS transistor switch within the smart card module, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The second terminal of the resistor may be connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
     The method may further comprise connecting the anode of the LED to a V BUS  supply voltage of the smart card module, connecting a first terminal of a resistor to the cathode of the LED, connecting a second terminal of the resistor to an I/O contact of the smart card module, connecting an NMOS transistor switch of a current switch circuit within the smart card module between the I/O contact and a GND reference voltage contact, and providing a modulated voltage source from the output of the output buffer that reflects the USB transaction activity to a gate terminal of the NMOS transistor switch within the smart card module, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The second terminal of the resistor may be connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
     A further embodiment of the present invention is a device comprising transceivers positioned within the smart card module for transmitting and receiving USB packets comprising differential serial signals between the USB port and external terminals of transceivers, the transceivers having internal terminals connected to inputs of a serial engine positioned within the smart card module, a correct transfer signal from an output of the serial engine interconnected to a micro-controller and a counter, both positioned within the smart card module, the counter being controlled from the micro-controller, an output of the counter driving an input of an output buffer positioned within the smart card module, and a device activated from an output of the output buffer for signaling transaction activity based on the correct transfer signal. The device being activated may be a LED, having an anode and a cathode. 
     The device may further include the anode of the LED connected to a V BUS  supply voltage of the smart card module, the cathode of the LED connected to an I/O contact of the smart card module, a second NMOS transistor of a current mirror circuit within the smart card module connected between the I/O contact and a GND reference voltage contact for providing a modulated current sink for illumination of the LED, a first NMOS transistor of the current mirror circuit within the smart card module connected to the second NMOS transistor, and a modulated current provided to the first NMOS transistor from the output of the output buffer that reflects the USB transaction activity, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The cathode of the LED may be connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
     The device may further comprise the anode of the LED connected to an I/O contact of the smart card module, the cathode of the LED connected to a GND reference voltage of the smart card module, a second PMOS transistor of a current mirror circuit within the smart card module connected between the I/O contact and a V BUS  supply voltage contact for providing a modulated current sink for illumination of the LED, a first PMOS transistor of the current mirror circuit within the smart card module connected to the second PMOS transistor, and a modulated current provided to the first PMOS transistor from the output of the output buffer that reflects the USB transaction activity, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The anode of the LED is connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
     The device may further comprise the cathode of the LED connected to a GND reference voltage of the smart card module, a first terminal of a resistor connected to the anode of the LED, a second terminal of the resistor connected to an I/O contact of the smart card module, a PMOS transistor switch of a current switch circuit within the smart card module connected between the I/O contact and a V BUS  supply voltage contact, and a modulated voltage source provided from the output of the output buffer that reflects the USB transaction activity to a gate terminal of the PMOS transistor switch within the smart card module, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The second terminal of the resistor is connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
     The device may further include the anode of the LED connected to a V BUS  supply voltage of the smart card module, a first terminal of a resistor connected to the cathode of the LED, a second terminal of the resistor connected to an I/O contact of the smart card module, an NMOS transistor switch of a current switch circuit within the smart card module connected between the I/O contact and a GND reference voltage contact, and a modulated voltage source provided from the output of the output buffer that reflects the USB transaction activity to a gate terminal of the NMOS transistor switch within the smart card module, causing the illumination intensity of the LED to be modulated according to the USB transaction activity. The second terminal of the resistor may be connected to a contact of the smart card module selected from the group consisting of C 2 , C 3 , C 6  and C 7 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become understood with regard to the following description, appended claims, and accompanying drawings where: 
     FIG. 1 shows a smart card module that is compatible with a USB smart card for connecting to a USB serial link; 
     FIG. 2 shows a block diagram of a ISO standard smart card reader and a smart card; 
     FIG. 3 shows a block diagram of a novel IC having USB transceivers and USB traffic signaling circuits; 
     FIG. 4 shows a USB smart card reader and a smart card; 
     FIG. 5 shows a USB interface connection between a USB smart card module and a USB port using a cable and driving a LED to indicate USB traffic activity; 
     FIG. 6 shows a USB smart card module plug ready to be separated from a USB smart card; 
     FIG. 7 shows a USB style token reader with a USB smart card module plug inserted; 
     FIG. 8 shows a USB interface connection between a USB smart card module within a token reader and a USB port using a plug connector and driving a LED to indicate USB traffic activity; 
     FIG. 9 shows the electrical schematic of the USB traffic signaling LED biased by a current sink to GND reference voltage; 
     FIG. 10 shows the electrical schematic of the USB traffic signaling LED biased by a current source from V BUS ; 
     FIG. 11 shows the electrical schematic of the USB traffic signaling LED enabled by a switch to V BUS ; and 
     FIG. 12 shows the electrical schematic of the USB traffic signaling LED enabled by a switch to GND reference voltage. 
    
    
     DETAILED DESCRIPTION 
     Turning to FIG. 1, FIG. 1 shows a smart card module  10  that is compatible with ISO7816-2 Dimension and Location of the Contacts. The smart card module  10  has eight electrical contacts  1 - 8  positioned on a substrate  11  and an IC  100  attached to the side of the substrate  11  opposite the contacts  1 - 8 . The electrical contacts  1 - 8  are electrically isolated from each other. Electrical connections between the IC  100  and the contacts  1 - 8  are accomplished through the use of bonding wires  9 . Electrical connections between the opposite sides of the substrate  11  may be accomplished by any means common in the art, including conductive vias. The IC  100  and the bonding wires  9  are normally encapsulated for protection from mechanical and environmental effects. The smart card module  10  is compatible for use in asynchronous ISO 7816 applications. Contact C 1   1  is assigned to the Supply voltage VCC, contact C 2   2  is assigned to the Reset signal RST, contact C 3   3  is assigned to the Clock signal CLK, contact C 5   5  is assigned to the GND reference voltage, contact C 6   6  is assigned to the Variable supply voltage VPP  6  and contact C 7   7  is assigned to Data input/output I/O. In synchronous ISO7816-10 applications contact C 4   4  is assigned to function code FCB and contact C 8   8  may also be used for other synchronous applications. The smart card module  10  is compatible for use in USB applications. In a USB smart card application. Contact C 1   1  is assigned to the Supply voltage V BUS , contact C 4   4  is assigned to the Data line D+, contact C 5   5  is assigned to the GND reference voltage, contact C 8   8  is assigned to the Data line D−. Contacts C 2   2 , C 3   3 , C 6   6  and C 7   7  are available for other uses. The present invention consists of the use of one contact of C 2 , C 3 , C 6  and C 7  module contacts to report the USB activities between the computer-based application and the USB smart card IC  100 . 
     Turning to FIG. 2, FIG. 2 shows a block diagram of an ISO standard smart card reader  20 . The smart card reader  20  is connected to a computer  21 . A smart card  200  is inserted in the smart card reader  20 . The protocol used between the smart card  200  and the smart card reader  20  is described by the ISO7816 standard. This protocol is not embedded in the computer  21 . When the smart card  200  is inserted in the smart card reader  20 , a smart card module  10  is connected to a smart card first interface  26  using a pass-through connector  27 . The first interface  26  masters the half-duplex ISO7816 protocol. The smart card reader  20  is connected to the computer parallel port  22 , serial port  23  or even a USB port  24  through a second interface  25 . An LED  300 , driven by hardware circuitry in the smart card reader  20 , provides an indication of any traffic between the smart card and the computer. 
     Turning now to FIG. 3, FIG. 3 shows a block diagram of a novel IC  100  having USB transceivers  36  and USB traffic signaling circuits  31 ,  32 . FIG. 3 depicts one particular embodiment of the present invention. The USB transceiver  36  receives differential serial signals D+ and D−, and communicates with a serial engine  35 . The serial engine  35  exchanges data with a micro-controller  34 . A software program is stored in a memory  33 . Every time a USB packet is transferred upstream or downstream with success, a Correct Transfer (CTR) signal  37 , connected between the serial engine  35 , the micro-controller  34  and a counter  32 , is set by the serial engine hardware  35 . A successful transfer occurs when no error is detected in a packet transfer. The software program stored in the memory  33  causes the micro-controller  34  to clear the CTR signal  37  once a CTR interrupt is serviced by the micro-controller  34 . The counter  32  has, for example, ten stages. The software program stored in the memory  33  causes the micro-controller  34  to select an appropriate output of the counter  32  via the select signal  38 . The selected output of the counter  32  activates the LED driver  31 , connected to the I/O pad  39 . 
     Turning now to FIG. 4, FIG. 4 shows a smart card reader  40  and a smart card  200 . The smart card  200  contains a smart card module  10  as described earlier. The smart card  200  plugs into the smart card reader  40 . The smart card reader  40  has connecting contacts of a pass-through connector  27  that connect the smart card module contacts to a USB cable  42  terminated by a USB series A plug  41 . The USB series A plug connects to a USB Hub port  24  on a Host PC  21  or other USB hub. A LED  300  is mounted on the USB card reader in addition to the pass-through connector  27 . No other active components are required in the USB smart card reader. The USB compatible smart card  200  inserted in the USB style smart card reader  40  terminated by the USB series A plug connector  41  constitute a USB smart card device  43 . 
     Turning now to FIG. 5, FIG. 5 shows a USB interface connection between a USB smart card module  10  and a USB port  24  using a cable  42  and driving a LED  300  to indicate USB traffic activity, as physically depicted in FIG.  4 . Eight pass-through connector pins  50  within the smart card reader  40  connect to the contacts on the smart card module  10 . The electrical connections from the smart card module are carried via the cable  42  to a USB Series A plug connector  41 . The USB compatible smart card module  10  is inserted in the USB style smart card reader  40  equipped with the USB cable  42  terminated by the USB series A plug connector  41 . The cable  42  utilizes four wires for connecting the smart card module  10  to the plug connector  41 . The connector  41  may plug directly into a USB port  24  of a Host PC  21  root hub equipped with a Series A receptacle or a USB port of a hub equipped with the same receptacle as depicted in FIG.  4 . The hub provides the V BUS  power supply connected to the contact C 1   1  on the smart card module  10 , the GND reference voltage connected to the contact C 5   5  on the smart card module  10 , the Data line D+ connected to the contact C 4   4  and the Data line D− connected to the contact C 8   8 . In the present embodiment of the invention, when a smart card is connected to a USB interface, the smart card module contacts C 2 , C 3 , and C 6  are not assigned. The anode of a LED  300  is connected to the contact C 7   7  of the smart card module  10  and the cathode of the LED  300  is connected to the GND reference voltage of the smart card module  10 . A USB style card reader will normally provide these signals to the smart card module according to the electrical and transmission protocols defined in the USB specification. While the present embodiment of the invention makes use of contact C 4   4  and contact C 8   8 , the ISO 7816-2standard reserves these two contacts for future use. The ISO 7816-10 assigns C 4  to Function code FCB in synchronous application. 
     Turning now to FIG. 6, FIG. 6 shows a USB smart card module plug  400  ready to be separated from a USB smart card  200 . A smart card module  10  is positioned on the smart card module plug  400 . This is another form factor of a USB smart card  200 . When the smart card module plug  400  is separated from the smart card  200 , it may be inserted into a USB token reader  500  as shown in FIG.  7 . 
     Turning to FIG. 7, FIG. 7 shows a token reader  500  with a plug module  400  inserted. This type of module plug  400  is widely used in SIM applications designed for GSM telephones. The connector  41  may plug directly into a USB port  24  of a Host PC  21  root hub equipped with a Series A receptacle or a USB port of a hub equipped with the same receptacle, as depicted in FIG.  4 . The electrical configuration of the smart card module  10  positioned on the smart card module plug  400  in the token reader  500  is the same as that depicted in FIG. 5, except that the plug connector  41  is attached to the token reader  500  rather than the cable  42 . The USB compatible smart card module plug  400  inserted in the USB style smart card reader  500  terminated by the USB series A plug connector  41  constitute a USB smart card device  46 . 
     Turning now to FIG. 8, FIG. 8 shows a USB interface connection between a USB smart card module  10  within a token reader  500  and a USB port  24  using a plug connector  41  and driving a LED  300  to indicate USB traffic activity, as physically depicted in FIG.  7 . Eight pass-through connector pins  50  within the token reader  500  connect to the contacts on the smart card module  10 . The electrical connections from the smart card module  10  are connected to a USB Series A plug connector  41 . The USB compatible smart card module  10  is inserted in a USB style token reader  500  terminated by the USB series A plug connector  41 . The connector  41  may plug directly into a USB port  24  of a Host PC  21  root hub equipped with a series A receptacle or a USB port of a hub equipped with the same receptacle as depicted in FIG. 4 . The hub provides the V BUS  power supply connected to the contact C 1   1  on the smart card module  10 , the GND reference voltage connected to the contact C 5   5  on the smart card module  10 , the Data signal D+ connected to the contact C 4   4  on the smart card module  10 , and the Data signal D− connected to the contact C 8   8  on the smart card module  10 . The anode of a LED  300  is connected to the contact C 7  of the smart card module  10  and the cathode of the LED is connected to the GND reference voltage of the smart card module  10 . A USB style token reader will normally provide these signals to the smart card module according to the electrical and transmission protocols defined in the USB specification. In the present embodiment of the invention the smart card module contacts C 2 , C 3 , and C 6  are not assigned. While the present embodiment of the invention makes use of contact C 4   4  and contact C 8   8 , the ISO 7816-2 standard reserves these two contacts for future use. The ISO 7816-10 assigns C 4  to Function code FCB in synchronous application. 
     Turning now to FIG. 9, FIG. 9 shows the electrical schematic  60  of the USB traffic signaling LED  300  biased by a current source to contact C 5   5 . The current source circuit is part of the IC  100  mounted on the smart card module  10 . FIG. 9 depicts a current mirror circuit  60  that comprises NMOS transistors  63 ,  64  that enable the current in the LED  300  to be determined by the current  62  into the NMOS transistor  63 , such that the current  62  into the NMOS transistor  63  is proportional to the current through the NMOS transistor  64  that flows through the LED  300 . Current mirror circuits and their operation are well known to skilled practitioners of the electronics art. The NMOS transistor  64  is connected between the contact C 7   7  and the contact C 5   5 . The LED  300  is connected between the supply voltage V BUS  and the contact C 7   7 , the anode of the LED  300  being connected to V BUS  and the cathode of the LED  300  being connected to the contact C 7   7 . The current  62 , and hence current through the LED  300 , determines the brightness of the LED  300 , and is a function of the amount of USB traffic. 
     Turning now to FIG. 10, FIG. 10 shows the electrical schematic  70  of the USB traffic signaling LED  300  biased by a current source from contact C 1   1 . The current source circuit is part of the IC  100  mounted on the smart card module  10 . FIG. 10 depicts a current mirror circuit  70  that comprises PMOS transistors  73 ,  74  that enable the current in the LED  300  to be determined by the current  72  into the PMOS transistor  73 , such that the current  72  into the PMOS transistor  73  is proportional to the current through the PMOS transistor  74  that flows through the LED  300 . Current mirror circuits and their operation are well known to skilled practitioners of the electronics art. The PMOS transistor  74  is connected between the I/O contact  7  and the contact C 1   1 . The LED  300  is connected between the GND reference voltage and the contact C 7   7 , the anode of the LED  300  being connected to the contact C 7   7  and the cathode of the LED  300  being connected to GND reference voltage . The current  72 , and hence current through the LED  300 , determines the brightness of the LED  300 , and is a function of the amount of USB traffic. 
     Turning now to FIG. 11, FIG. 11 shows the electrical schematic  80  of the USB traffic signaling LED  300  enabled by a current switch from contact C 1   1  . The current switch circuit is part of the IC  100  mounted on the smart card module  10 . FIG. 11 depicts a voltage switch circuit  80  comprising a PMOS transistor switch  83  connected between the contact C 7   7  and the contact C 1   1 . A series circuit consisting of an LED  300  and a resistor  11  is connected between GND reference voltage and the contact C 7   7 , the cathode of the LED  300  being connected to GND reference voltage. When a negative voltage is applied to the gate  82  of the PMOS transistor  83 , it is switched on, causing current to flow from the contact C 7   7  through the resistor  11  and the LED  300  to the GND reference voltage. The resistor  11  limits the current through the LED  300 . The modulation of the voltage at the gate  82  of the PMOS transistor  83  is a function of the USB traffic, making the brightness of the LED  300 , a function of the amount of USB traffic. 
     Turning now to FIG. 12, FIG. 12 shows the electrical schematic  90  of the USB traffic signaling LED  300  enabled by a current switch to the contact C 5   5 . The current switch circuit is part of the IC  100  mounted on the smart card module  10 . FIG. 12 depicts a voltage switch circuit  90  comprising an NMOS transistor switch  93  connected between the contact C 7   7  and the contact C 5   5 . A series circuit consisting of an LED  300  and a resistor  12  is connected between the supply voltage V BUS  and the contact C 7   7 , the anode of the LED  300  being connected to V BUS . When a positive voltage is applied to the gate  92  of the NMOS transistor  93 , it is switched on, causing current to flow through the LED  300  and the resistor  12  to the GND reference voltage. The resistor  12  limits the current through the LED  300 . The modulation of the voltage at the gate  92  of the NMOS transistor  93  is a function of the USB traffic, making the brightness of the LED  300 , a function of the amount of USB traffic. Although the present invention has been described in detail with reference to certain preferred embodiments, it should be apparent that modifications and adaptations to those embodiments may occur to persons skilled in the art without departing from the spirit and scope of the present invention as set forth in the following claims.