Abstract: Dummy data wires or PCB tracks are employed that run close to and parallel with the wires or tracks that carry the actual data between the card and the microprocessor. These dummy data tracks or wires are driven with dummy random data at a similar data rate to that used on the real data track(s) or wire(s). As the dummy tracks or wires are close to the “real” data tracks or wires and the dummy data is random, attempts to capacitively sense the actual data will be disrupted. To counter this method of detection the dummy data track may be connected to loads (resistive, capacitive or both) to ensure that current flows when dummy data is applied to the tracks. The loads may be selected such that the current flows are similar to those in the real data track. This is achieved by determining the terminating impedances on the real data track and using similar values on the dummy data tracks.

Abstract: A card reader terminal is provided with circuitry to detect wireless transmission of data from the card terminal from illicit transmitting equipment within the terminal in the form of a “shim” or otherwise. The detector circuit is connected to an A/D input of a microprocessor. Voltage level at the input may be measured rather than just treating it as digital input where the voltage level would be taken by the processor as either ON (signal present) or OFF (signal not present). Where the microprocessor (or other processing electronics) used does not have an analog to digital converter input, an external analog to digital circuit may be used. The terminal can determine the level of radio signal activity in its vicinity before a card is entered into the card slot, the level after the card is inserted and the level during the time the terminal is exchanging data with the card.

Abstract: The present invention detects the current flowing through the contacts of the smart card reader due to the presence of a “shim”. Small value resistors are connected in series with either the Power connection or the Ground connection, or both. Values are typically 47 milliohms to 100 milliohms. The use of such small values ensures that little voltage is dropped across the resistors and that the card is therefore adequately powered. With no card present, the current through these resistors should be zero and therefore the voltage across the resistors will also be zero. Amplifier circuits are employed to monitor and amplify the voltage across the resistors and in the “PayPod” design the amplifier outputs are connected to analogue to digital inputs on the microprocessor. Where the microprocessor (or other processing electronics) used has no analogue to digital inputs, separate analogue to digital circuits may be used.

Abstract: A multi-layer Printed Circuit Board (PCB) holds a number of sections of serpentine track on two or more internal layers of a multi-layer PCB. The sections are connected in series with resistors between each section. One end of each of the resistors a connection to an analogue to digital converter is made. In its simplest form, each of the serpentine track is produced on a separate internal layer of the PCB. The outer layers are typically ground planes. Attempts to drill through the PCB are likely to short the ground plane to one or more of the internal serpentine tracks, which will alter the voltages on the analogue to digital connections. Shorting out sections of serpentine track with a view to then drilling through undetected are made very difficult in this scheme since shorting any tack to the ground plane or any track to any other track or breaking any track will be detected by changes to the voltages on the connections to the analogue to digital converter inputs.