Abstract: A method of manipulating a calculator comprises steps of selecting a desired instruction card, associating/attaching the instruction card to the calculator, and manipulating the special function keys according to the instructions. A set of auxiliary cards, having manipulation instructions, formula/equations, and manipulation principles printed thereon, can be attached to the calculator for achieving the method of manipulation.

Abstract: The present invention relates to an improved calculator housing which includes a number-entry key housing having two lugs extending longitudinally from its upper ends, each with a first annular boss projecting inwardly from the lugs; a display housing having a hollow cylindrical extension portion with a circular protrusion at one of its end and a second boss at the other end, which extends between the lugs of the number-entry key housing; both the circular protrusion and the second annular boss being movably inserted into the first annular bosses, and means for interengaging the first and second annular bosses to limit the movement of the second annular boss relative to the second annular boss so that the display housing can be folded relative to the number-entry key housing adjusted and fixed in a suitable position according to the user's need, for seeing the display clearly and comfortably in practical use.

Abstract: The present invention disclosed an improved calculator structure comprising a casing which has an operating panel, a calculating circuit board disposed in the casing, and a plurality of keys mounted on the calculating circuit board and extending out of the operating panel of the casing, in which an elongated answer bar is provided along the front end of the calculator, and the length of the answer bar approximates the width of the calculator.

Abstract: A telephone set control device. A dialing signal is converted into a pulse signal through a converter circuit; then, a pulse detection circuit generates a constant wavewidth signal to be coupled to a microprocessor unit, which then generates a signal, by means of the program instruction set in a read-only memory and A/D-latch circuits to operate a converter circuit to cut off the telephone connection at the end of a pre-programmed time period. The device enables the telephone owner to preselect the talking time and the number of digits to be dialed. The talking time and the number of digits which may be dialed are set in advance via a selective switch control means so as to let the user dial only the number of digits preselected and talk for only the period of time set; thereby saving time and preventing others from dialing unauthorized numbers.