| 摘要 |
<p>A lock and key for use by waiters in large establishments to gain access to dispensers which charge the extracted article to the individual waiter uses a flat key pref. made of polycarbonate which has in the centre of the ward a copper foil, bonded to a self-adhesive plastic foil. This copper foil is impermeable for infrared rays but two rows of holes, each with up to 12 holes, allow a coded identification. The lock itself is a block of plastics, with a slot for the key and with cross bores to correspond to the rows in the copper foil of the keys. One end of each cross bore carries an infrared diode and the other an infrared silicon transistor as the radiation detector. This creates a system which cannot be counterfeited and is less bulky than one using reed relays.</p> |
