Plessey Overseas Limited

Siemens Corporation

Anthony John Salloway

Kevin Jonathan Hickman

Geoffrey M Garner

Robert C Twiney

A method of measuring a level of liquid cryogen, comprising the steps of immersing a liquid cryogen level probe in a liquid cryogen, applying a propagation current to the heater () to induce quench in at least an adjacent part of the superconductive material (); removing the propagation current from the heater; applying a measurement current to the superconductive material; and measuring () a voltage across the superconductive material thereby to determine the level of the liquid cryogen. In articular, the method comprises the steps of monitoring () the voltage across the superconductive material while the propagation current is being applied; and ceasing application of the propagation current in response to the detection of a voltage across the superconductive material which exceeds a certain threshold level.

Method for measuring liquid cryogen level using a level probe

Noise reduction system

A telephone subscriber subset including a transducer for generating audible signalling tone information in which the signalling tones are received at the input terminal as substantially sinusoidal electrical waveforms and including a converter within the handset for conversion of the signalling tones to a substantially non-sinusoidal electrical waveforms before feeding to the transducer.

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Northampton, United Kingdom

Anthony John Salloway