Abstract: This invention relates to a method and system for verifying authenticity safe against forgery of an object releasing a function said object being of base material having random imperfections in or on the same, comprising measuring random imperfections in or on the base material of said object in a predetermined measuring track over the surface of said object of base material having random imperfections in or on the same by means of a detector for detecting said random imperfections, said random imperfections optionally being supplied to said base material, converting said measured random imperfections into pulses, supplying said pulses together with timing pulses to an AND gate, whereby only simultaneously arriving pulses are passed, supplying said passed pulses to a shift register shifting with said timing pulses to obtain a binary code, comparing said binary code with a previously stored binary code of the same object, whereby the function is released if said binary codes are identical; as well as a system

Abstract: This hands-free telephone prevents acoustic feedback between its speaker and microphone by attenuating either the transmission or receive path under the control of a corresponding pair of counters (computers), each counter sensing the signal divided and digitized from its corresponding path. An increase in counted pulses indicates feedback and causes a counter to more quickly reach a predetermined counter state (count), to trigger attenuation (damping) before it can be reset (restored) to zero by the other counter.

Abstract: A hands-free telephone set has both transmit and receive channels open for the reception of signals, while still inhibiting feedback-singing. Two switched attenuators are provided in cascade in each channel. The first attenuator is switched after a syllable delay, and the second attenuator is switched after a yet longer delay.

Abstract: A method of manufacturing documents such as paper money, credit cards, identification cards and the like in a manner so as to prevent forgeries thereof, comprises the steps of producing a base material, coating fibers with a magnetic or magnetizable material, and embedding the fibers into the base material during the production of the base material; an apparatus for checking the authenticity of documents such as paper money, credit cards, identification cards, and the like comprises in combination a document having fibers which are coated with a magnetic or magnetizable material embedded therein, detecting means for scanning the document to determine the number of magnetic particles present in the document, and means for moving the document and the detecting means relative to each other so as to provide a scanning trace, the document and the detecting means being disposed in a close relationship to each other.