| 摘要 |
In a circuit arrangement for detecting and distinguishing frequency-determined remote control signals, particularly pulse series of various different frequencies in infrared remote controls, a switching mechanism can be operated by each pulse obtained from the received signal in a fixed ratio to its frequency for detecting the remote control signals and dividing them into channels, as long as the voltage across a capacitor which can be charged up via the switches of the switching mechanism with different currents for each step which rise in the order of switching, and the discharge of which is caused by each of these pulses, has not reached a particular threshold value before the arrival of the next pulse, the reaching of this threshold value due to the interaction of capacitor charging current and capacitor capacitance over the time required for this being a measure of the frequency of the pulse sequence, here for the transgression below the upper frequency limit of the receiving channel provided for the existing switching position, and thus initially indicates the selection of the correct frequency channel by means of the position of the switching mechanism reached during this process. That the switching mechanism can be brought into a switching position which occurs in the order of switching between the two switching positions, one of which causes the charging of the capacitor with the highest and the other one of which causes the charging of the capacitor with the lowest of the currents possible by means of the switchable switching positions, if their positions were to include the switching mechanism, or into one of these two switching positions if the voltage across this capacitor reaches a further threshold value, the reaching of this threshold value due to the interaction of capacitor charging current and capacitor capacitance over the required time being a measure of the frequency of the pulse sequence, here for the transgression below the lower frequency limit of the receiving channel intended for the existing switching position, and thus indicates at least one missing pulse in the pulse sequence, which is otherwise regular for a remote control process, or the ending of the pulse sequence due to the non-arrival of a pulse before this threshold value is reached. <IMAGE>
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