Abstract: A thermal imaging device having both serial and parallel content is provided by a number of infra-red radiation detector strips supported side by side on an insulating substrate, each strip having a number of read-out regions. To allow connection from the side of the device to the innermost detector strips, conductors err end across outer strips. These conductors may extend over the strips and over insulating material therebetween. Alternatively the conductors may be in the form of conductive tracks embodied in a substrate of semiconductor material. The strips may be indented at the read-out regions to provide, with very close spacing, sufficient room for contact between the read-out regions and the conductive tracks. Preformed aluminium contact pads may be used between bridging links to the read-out regions and the conductive tracks the contact pads and preformed tracks being centered during preformation to ensure a good ohmic contact.

Abstract: A high sensitivity smoke detector comprises a cylindrical housing incorporating a sampling chamber through which air to be sampled is forced. A modulated light source, such as a laser, directs modulated light through the chamber to a beam dump. The light beam is offset from the axis of the housing by an acute angle of between 15 and 50 degrees. If any smoke particles are positioned within a sampling volume, the light is scattered along a path defined by baffles to an axially positioned light sensor whose electrical output is passed through a phase-sensitive detection circuit which is referenced by the frequency at which the light source is modulated, so as to produce an output dependent on the light scattered by the smoke particles.