Abstract: A device for making discs, comprising a press which includes at least one hydraulic pressure chamber, one wall of which is formed during operation by a flexible, thermally conductive plate which can be pressed against a thermoplastic substrate. The device comprises a first system of ducts which includes a pump whereby a hot liquid can be supplied to and discharged from the pressure chamber, and a second system of ducts which includes a pump whereby cold liquid can be supplied to the pressure chamber. The liquid in the systems of ducts and the pressure chamber is pressurized by means of an expansion vessel, the liquid part of which communicates with the pressure chamber as well as with both systems of ducts, its gas part communicating with a pressure control device.

Abstract: A transducer for measuring the amplitude of vibration of a member vibrating at a constant frequency. An outflow aperture is supplied from a compressed air supply, and opposite to the outflow aperture an obstructing element is arranged which can close the outflow aperture, the outflow aperture and element undergoing relative motion transverse to the direction of air flow. The average quantity of outflowing air is measured.