| 摘要 |
A holder for receiving a handset for photopolymerisation in the dental field is provided with a light barrier, the light transmitter (6) of which radiates light pulses which are at least one order of magnitude above the usual mains frequency; the photodiode used as light receiver (7) is followed by a high-pass filter (9, 10) which filters out pulses out of mains-operated light sources and noise pulses. Electrical signals obtained from the light pulses, after passing through the high-pass filter, are amplified and supplied to an integrating section (18, 19) via which a comparator (22) connected as Schmitt trigger is activated. <IMAGE>
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