Abstract: In a monitoring device including a reader and a data carrier, the data carrier includes a receiver coil (201), a resonator capacitor (202), rectifier means (203), a modulation capacitor (206), an energy storage capacitor (204), three modulation switches (209, 210, 211) and data processing means. The modulation capacitor (206), the energy storage capacitor (204), the data processing means and the three modulation switches (209, 210, 211) are arranged such that, in a first configuration, the modulation capacitor (206) and the energy storage capacitor (204) are coupled in parallel and, in a second configuration, the modulation capacitor (206) and the energy storage capacitor (204) are coupled in series. The invention further provides a method of operating a data carrier in such a monitoring device.

Abstract: In a monitoring device consisting of a reader and a data carrier, the reader (100) comprises a control unit (101), a memory (102), a digital signal generator (103), an output driver (104), resonance capacitors (105, 107) and a transmitter coil (106). The digital signal generator (103) is adapted for supplying a digital bit sequence selected among, at least two, bit sequences stored in the memory (102) whereby the strength of the magnetic field generated by the transmitter coil (106) can be varied dependent on the bit sequence selected by the control unit (101). The invention further provides a method of controlling the strength of a magnetic field generated by the reader of the monitoring device.

Abstract: In a monitoring device including a reader and a data carrier, the data carrier includes a receiver coil (201), a resonator capacitor (202), rectifier means (203), a modulation capacitor (206), an energy storage capacitor (204), three modulation switches (209, 210, 211) and data processing means. The modulation capacitor (206), the energy storage capacitor (204), the data processing means and the three modulation switches (209, 210, 211) are arranged such that, in a first configuration, the modulation capacitor (206) and the energy storage capacitor (204) are coupled in parallel and, in a second configuration, the modulation capacitor (206) and the energy storage capacitor (204) are coupled in series. The invention further provides a method of operating a data carrier in such a monitoring device.

Abstract: A hearing aid with beam forming properties, having at least two microphone channels (1a, 1b) for at least two microphones (2a, 2b), the microphone channels each comprising an analog to digital converter (3a, 3b) and having at least one programmable or program controlled signal processor (5), as well as a digital to analog converter, and at least one receiver and a battery for power supply. The hearing aid particularly comprises in each microphone channel (1a, 1b) a sigma-delta-type analog to digital converter (3a, 3b) including a digital low pas filter and a decimator 94) for converting a 1 Bit Stream of a high clock frequency into a digital word sequence of a lower clock frequency. At least one of the at least two microphone channels contains a controllable delay device (6) connected to the input side of the respective digital low pass filter and decimator (4) of the channel, the delay device (6) being controllable by the at least one signal processor (5).