Abstract: A method and apparatus for identifying an unknown gas by generating an infrared spectrum of the unknown gas using an infrared spectrophotometer that includes a circular variable interference filter, compressing the infrared spectrum of the unknown gas, and comparing the compressed infrared spectrum of the unknown gas to a library of compressed infrared spectra of reference compounds. After comparison, the compressed spectra that most closely match the unknown gas are decompressed and displayed. Because frequency characteristics of circular variable interference filters vary from filter to filter, information designating these frequency characteristics for the particular filter employed are used in generating the infrared spectrum of the unknown gas.

Abstract: A polymeric composition comprises:(i) an aromatic polyimide or an aromatic carboxylic ester polymer,(ii) a substantially wholly aliphatic polyamide, and(iii) a polyamide that contains both aromatic aliphatic moieties.It is found that the mechanical properties of blends of the aromatic polymers (i) and the polyamides (iii) can be significantly improved by the incorporation of a quantity of the aliphatic amides (ii), even though the miscibility of polymers, as observed by their glass transition temperatures may remain unchanged.

Abstract: Simple polarization independent wavelength tuning components (filters) employ a filter element, such as a Fabry-Perot etalon element, which is such that light input thereto undergoes two element transitions with orthogonal polarization states before being output, in order to suppress polarization noise. The element may be mounted for rotation about a single axis. In one arrangement, two etalon filters (20, 21), are separated by a half wave plate (22) providing the necessary polarization rotation. The two etalon filters and the half wave plate comprise a single element rotatable about the single axis.

Abstract: A 1.times.N single mode optical waveguide coupler comprises a single input optical fibre (1), a slab-like mixer waveguide (3) and a plurality (N) of output optical fibres (2). As a result of interference effects light introduced into the mixer waveguide (3) via the centrally located input fibre (1) produces a linear array of output spots at various intervals along the length of the mixer waveguide. The length of the mixer waveguide is chosen such that the output optical fibres are aligned with one such array of output spots. The fibres may be adiabatically tapered to a smaller diameter in order to increase their modal spot size.

Abstract: Apparatus whose measurement means consists solely of electronic components, measures the power taken by an electrical load connected to an alternating source of electricity supply in such a manner that the power sensed or energy accumulated is in agreement with the same measurements as performed by a conventional rotating disc electromechanical meter. Fundamental frequency filtering means when applied to either one or both supply voltage and load current ensure that the electronic circuitry performs the appropriate measurements in determining power consumption. A single sample per mains cycle applied to load current and supply voltage is sufficient to measure power consumption, energy consumption accumulation, and produce accumulated energy pulses appropriate to measurement of real power, true power and volt-ampere power consumed by the load.

Abstract: A gas detector for detecting a combination of at least three gasses employs an optical filter having a spectral passband shaped and positioned to produce substantially equal responses from a single detector to a given concentration of any single one of the gasses or to a concentration any two or more of the gasses. A filter spectrum encloses substantially equal areas of the absorption spectra of the gasses. The filter includes a spectral bandwidth, cut-on maximum wavelength, cut-on slope, cut-off maximum wavelength and cut-off slope, adjusted for controlling the areas of the gas absorption spectra enclosed therein.

Abstract: A television receiver is provided with a decoder (32) for decoding and displaying data which is included in a wide band video signal. In order to provide high resolution graphics, a processor (45) is connected to a data page store (41) of the decoder (32) and a program store (47). Instructions for the processor (45) are received `off air` and are stored in the store (41). The instructions are executed using programs stored in the store (47). A clock circuit (45a) is provided for the processor (45) to enable delays and other timed sequences to be introduced and a rounding circuit (46a) ensures as smooth an output display as possible. Data can additionally be received from another soce via a telephone line and selected for display in place of the `off air` data.