Abstract: Crystal oscillator and method which in one embodiment have a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, with the gain of the loop being maintained at a level of unity. Compensation is provided to offset the effects of shunt capacitance in the crystal element, and precise phase control is maintained around the loop. In other embodiments, a crystal element is connected in a series feedback loop with a buffer amplifier, and operation is provided by maintaining the oscillation signal at level at which distortion, clipping, and saturation do not occur. Compensation for shunt capacitance across the crystal element is provided by applying a compensation signal which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance.

Abstract: A refractory component which is vacuum-formed from ceramic fibres and which is to be mounted on the external casing or frame structure of a furnace to form part of heat-resisting lining is provided with an internal reinforcement in those parts of the component nearest the casing or frame structure and by which the component is to be mounted on the casing or frame structure. The reinforcement is embedded in the component during formation thereof and is of stiff open mesh form extending in a plane parallel to the general plane of the part of the casing or frame structure on which the component is mounted. The reinforcement is made from heat-resisting metal alloy, refractory clay or recrystallized alumina and is preferably of channel-section or other three dimensional form to increase its stiffness.