Abstract: A placido pattern 10 for use in obtaining a topography of an eye, includes a series of spaced arcuate segments 12 centered about a central point 14 and a series of spaced radial lines 16 emanating from the central point 14. Each pair of adjacent radial lines 16 defines a boundary of a portion of the arcuate segments 12.

Abstract: A placido pattern 10 for use in obtaining a topography of an eye, includes a series of spaced arcuate segments 12 centered about a central point 14 and a series of spaced radial lines 16 emanating from the central point 14. Each pair of adjacent radial lines 16 defines a boundary of a portion of the arcuate segments 12.

Abstract: A remotely controlled microphone amplifier has a first amplifier stage with a variable gain circuit operatively connected in the overall feedback loop of the first stage for controlling the gain in first increments. A unity gain second amplifier stage has variable attenuator operatively coupled between the output of the first amplifier stage and the input of the second amplifier stage. The variable attenuator controls the input to the second stage in second increments less than the first increments. The overall gain is linearly adjustable and varies in equal increments.

Abstract: A portable and collapsible seat which can be suspended on a flexible strap from the belt of a user including a rectangular base which ultimately constitutes the seat, a pair of spaced parallel flanges extending outwardly perpendicular to the base along the long edges of the base, a leg somewhat longer than the base itself pivotally and slidably connected to the base, the leg adapted to lie against the base in the collapsed condition of the seat and extending at right angles to the base or seat when the same is in the operable condition, a V-shaped link having a flattened portion adjacent its center and being curved at its ends, the flattened portion of the link being received in a hole in the leg between the ends of the leg, the curved ends of the link being received in openings in the flanges adjacent one end of the base, a clamp being provided at this one end of the base and formed by extensions of the flanges for holding the leg in the collapsed condition of the seat, a clip pivotally connected to the leg