Abstract: The invention relates to substitutes of real gems for the purpose of calibrating of commercial diamond testers and for verification of their correct operation. Suggested apparatus consists of a set of objects, which are made of cheap materials like brass, stainless steel, and electrically conductive rubber, and which exhibit combination of thermal and electric conductivities typical for diamonds and their popular imitations like moissanites, cubic zirconia, and others.

Abstract: The invention relates to devices which exhibit some physical properties, namely thermal conductivity and electrical resistance of diamonds and their popular imitations, and method for manufacturing and usage of such device. These physical properties of gems are usually used by commercial gem testers for the purpose of distinguishing true diamonds from the fakes. The imitations are made of inexpensive metals, like brass and stainless steel, and conductive plastics, and can replace more costly diamonds and other gems, like moissanite, white sapphire, and others for the purpose of verification of correct operation of gem testing devices.

Abstract: An asynchronous communication system includes a clock recovery circuit (2) to which the received signal (1) is applied and which provides recovered data (3) to a frame delimiter detector (4). The frame delimiter detector in turn generates a frame start signal to a frame sync generator (16) and provides asynchronous data (5) to an elastic buffer (7) which provides as its output the synchronized data (8). The clock recovery circuit also provides a recovered clock signal (9) to a clock guarding circuit (12). The clock guarding circuit (12) receives a local clock signal (11) and produces a guarded clock signal (13) and a data clock signal (14), both of which are supplied to the frame sync generator and the elastic buffer. The frame sync generator produces a frame sync signal having a duration determined by the active edges of the guarded clock and data clock signals, and this signal is used to load a mask pattern in the elastic buffer.