Abstract: The present invention relates broadly to any type of multi-layered, co-fired, ceramic-on-metal circuit board, as a new article of manufacture.The present invention is more specifically directed to various compositions of MgO-13 B.sub.2 O.sub.3 --SiO.sub.2 system glass-ceramics and compositions of such glass-ceramic and suitable fillers, which are suitable for use in the fabrication of multi-layered, co-fired, ceramic-on-metal circuit boards, in which the co-fired, multi-layered ceramic exhibits desirable electrical properties and a temperature coefficient of expansion which closely matches that of its co-fired metal base, although these compositions may have other uses.

Abstract: A plurality of current paths, each operating a fusible link, is connected between a common first terminal and different points along a resistor whose value is to be trimmed. By applying a constant voltage between this common terminal and a second terminal at one end of the resistor, fusible links in one or more of successive ones of the paths open, effectively placing successively greater values resistance between the first and second terminals, thereby successively reducing the amount of current flow between these terminals. When the current drops to lower than a given value, no further links open and the value of the resistance between the terminals is in the desired range.

Abstract: A high-Q printed circuit board inductance comprises a ferromagnetic core placed through an aperture of a metallic support base of a printed circuit board. The ferromagnetic core provides a preferred path for time-varying magnetic flux. An overlayer of insulating material such as porcelain enamel is interposed between a planar printed coil structure located about the ferromagnetic core and the metallic support base. A gap is formed in the metallic support base and extends outwardly from the aperture in a manner intersecting closed paths within the metallic support base that are linked by the time-varying magnetic flux. A high-Q inductance is formed because the flow of eddy currents in the closed paths is substantially impeded across the gap.