Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1998-08-07
2000-01-04
Wu, Daniel J.
Communications: electrical
Condition responsive indicating system
Specific condition
3408253, 340540, 367 93, 367 95, G08B 1318
Patent
active
060114703
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the detection of an object covering the surface of a keyboard.
2. Related Art
Self-operating apparatuses have, as a rule, a keyboard on which the user inputs confidential or secret data, especially a secret number designated as PIN (personal identification number). In order to access these and similar data illegally, a keyboard can be manipulated by superposed similar keyboards or other objects. An arrangement which discovers such manipulations must, however, simultaneously be unobtrusive, sturdy, and be secured against wanton damage (vandalism).
It is the problem of the invention, therefore, to give a corresponding arrangement.
SUMMARY OF THE INVENTION
The invention solves the problem by a sound generator, preferably a sound generator, mounted in the interior of the keyboard. The generator radiates a signal, preferably ultrasonic waves, through the surface of the keyboard. Above the keyboard there can be mounted a receiver which detects the radiated ultrasonic waves and, accordingly, signals a proper state after processing the signal with an evaluating circuit connected to a control that can block the keyboard or an apparatus containing the keyboard in response to an improper state. The protective arrangement is thus unobtrusive and, further, protected against vandalism.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 shows an arrangement of a keyboard with ultrasonic transmitter and receiver;
FIG. 2 shows a possible arrangement of an ultrasonic transmitter in the frame of a keyboard.
DETAILED DESCRIPTION
Much simplified, and schematically, there is shown in FIG. 1 a keyboard on base plate 10 under a hood 13. The keyboard consists of a key frame 11 and individually keys 12a-d. In the interior of the keyboard there is mounted on the underside of the keyboard frame 11 on a bridge between the keys 12a-d, an ultrasonic transmitter 14, which is electrically actuated. Above the keyboard, in the example in the hood 13 protecting the keyboard, an ultrasonic receiver 15 is mounted. The signal received by it is amplified, rectified and fed to a threshold value detector.
These arrangements are executed in a known manner and are not represented in FIG. 1. The output of the threshold value detector is connected with a control unit for the apparatus using the keyboard as input apparatus. As long as the detector for the threshold value of the control unit reports the presence of a signal, the apparatus is ready for operation, and it uses the keyboard as input apparatus.
A sheet of paper laid on the keyboard already dampens the relation of the ultrasonic generator 14 significantly. The threshold value detector therefore alters its signal to the control unit, which reacts correspondingly. If the apparatus is in the state of readiness for operation, then a loss of the ultrasonic transmission reported by the threshold value detector is interpreted as manipulation, and the apparatus is shifted into a disturbance state. This does not hold if a user was just then asked to input data, since the weakening can originate from the hand of the user. The apparatus is protected, therefore, by the means that before the start of each transaction by an operator of the keyboard, the threshold value detector must report the presence of a signal. There the ultrasonic generator in the keyboard is preferably mounted on the inner surface of a key or of a key frame. In many cases the material is acoustically thin enough so that from the keyboard, without further measures, a well-detectable signal is radiated, without the presence of the ultrasound generator becoming visible. Since the surface of the keyboard is undisturbed, neither can it be simply perceived where the signal is radiated, so that attempts at manipulation are made difficult.
In keyboards with solid metal keyboard frame, in correspondence to FIG. 2, into a bridge of the key frame 11 a blind hole is made from inside, so that the ultrasonic waves can emerge through the remaining materi
REFERENCES:
patent: 5149986 (1992-09-01), Jalbert
patent: 5438318 (1995-08-01), Latorre et al.
patent: 5757271 (1998-05-01), Andrews
Liedtke Oliver
Schulte Johannes
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