Abstract: A self-corrective, reversible device comprising a handled, slotted framework, on each side of which the top frame is imprinted with inverse mathematical symbols, below which is a number line from one through ten in ascending and descending order. Below the number line, nine channeled horizontal rows each contain ten grooved, colored, movable, workpieces. The first four rows on side "A" teach counting, addition, subtraction and place value. These workpieces have the following values: Row one, "1" each; Row two, "1" each; Row three, "10" each and Row four, "100" each. Workpieces in each row are the same color, but each row is a different color. Corresponding with these four rows in both value and color are four boxes imprinted on an erasable surface contained within the framework. The remaining five rows on side "A" teach large and small letters of the alphabet, phonics and consonant blends.

Abstract: A portable and foldable teaching aid combines an abacus and an inclined writing surface. The abacus helps teach math skills and the inclined writing surface helps strengthen hand and wrist muscles that are used in writing. The abacus and writing board are positioned in physical proximity to one another to encourage children to write down math problems on the writing board, to solve them on the abacus, and to write down the answer on the writing board. The writing board may be of the dry erase type, the chalkboard type, or any other suitable, erasable writing surface. It may also be magnetized to hold letters, shapes, and the like. The writing board is releasably attached to support rods so that it can be separated from them when the device is folded for storage. When folded, it can be carried separately or placed into a child's backpack.

Abstract: A book that can be customized to teach letters, numbers, a series of letters, for example, a word such as a child's name and the like. The front cover has a window or opening through which can be seen the letters. The series of letters is formed by cutting each page short enough than the page beneath it such that letters on the right edge form the series.

Abstract: An etchant of PSG (14) or BPSG with high selectivity to substantially undoped oxide (12) includes a fluorine-liberating compound and a fluorine-scavenging compound. The fluorine-liberating compound is preferably a perfluorinated inorganic compound, and the fluorine-scavenging compound is preferably a hydrogen-liberating compound such as hydrogen. A particularly preferred inorganic fluorine-liberating compound is nitrogen trifluoride. In an exemplary embodiment, etch rate ratios of PSG to undoped oxide as high as 11 to 1 were obtained.

Abstract: An apparatus for teaching mathematics which applies and puts to work in various ways the modern teaching of mathematics for all levels of elementary education through set theory, comprises a horizontal board divided into eleven zones and having two outwardly-projecting subsidiary boards. In use, objects can be placed in selected zones of the horizontal board to demonstrate mathematical operations, and information relating to the operation is written on appropriate zones of the vertical board and on the subsidiary boards. The horizontal board has a bevelled front edge portion on which further information can be written, and two portions in which objects to be placed in the zones of the horizontal board can be placed beforehand.

Abstract: An optically linked calculator system for displaying data generated by a local calculator at both the local calculator and at a detached display. The calculator system includes a plurality of transmitting calculators and receiving units. The receiving units include remote display receiving units and receiving calculators. Transmitting calculators transmit entered data and calculated results. Receiving units receive and display transmitted data entries and calculated results. A calculator includes a keyboard, keyboard logic, processing logic, display, display logic, transmit logic, infrared transmitter, switching means, infrared receiver receiver logic and converting logic. The switching means selectively enables components of the calculator for effecting a transmit mode, receive mode, and calculate mode. The remote receiver display unit includes an infrared receiver, data detection logic, processing logic, and a display.

Abstract: A board-type device for use in teaching children the alphabet, numbes, how to tell time, and the like. The device includes a disk-like, double sided chalkboard member and a ring-like frame member extending completely about the periphery of the blackboard member with the blackboard member rotatably mounted to the frame member. Alphabetic letters and the like are located about the frame member on one side thereof. Numerals and the like may be located about the other side of the frame member with the numerals arranged similar to a clock face. Pointers are attached to both sides of the chalkboard member whereby rotation of the chalkboard member will cause the pointers to point towards various specific letters and/or numbers and/or the like, etc. Indicia-bearing inserts are rotatably attached to the front and back surfaces of the frame.