Abstract: A power supply system for a dynamic memory includes a main power supply, a backup power supply and a power down detection circuit which are all connected in parallel across the input of a DC/DC converter. In turn the DC/DC converter supplies regulated power to the dynamic memory. On interruption of the main power supply, the backup supply provides input power to the DC/DC converter only as long as the power sensed by the power down detection circuit is adequate for the DC/DC converter to maintain a bit pattern stored in the dynamic memory. On sensing inadequate input power to the DC/DC converter the backup supply is automatically disconnected.

Abstract: A combination of an npn transistor, a pnp transistor and associated circuitry is utilized to provide a threshold amplifier which has a variable threshold. The voltage level at the emitter of the npn transistor, when the npn transistor is off, determines the variable threshold. A second pnp transistor is preferably utilized to provide a means by which the threshold voltage can be set to a very low voltage level.

Abstract: A normal video signal and an overlay video signal are combined by supplying the normal video signal to the base of a first emitter follower transistor while the overlay video signal is supplied to the base of a second emitter follower transistor. The two transistors are biased such that the first transistor is at a slightly lower voltage than the second (overlay) transistor and is reversed biased (off) any time data is available from the overlay video signal.

Abstract: The size of an object in the field of view of a television camera or other device which can create an image of an object is determined by generating a calibrated grid for a video display in response to a measurement of the distance between the image creating device and the object itself. Both the object and the grid may be displayed on a video display means in such a manner that the object is overlaid with the calibrated grid. The length of the lines in the calibrated grid or the distance between points in the calibrated grid, as actually displayed, will be representative of a particular distance and thus an observer viewing the video display can determine the actual size of the object by using the calibrated grid to actually measure the object.

Abstract: An electrical circuit is provided for converting the output from a keyboard into a binary form. At least two priority encoders are interfaced to the keyboard. Each priority encoder generates a binary code when a particular key is depressed. The individual binary outputs from the priority encoders are combined to provide a binary output which is representative of the particular key which has been depressed. In this manner, the output of the keyboard is encoded to binary form. The keyboard encoding system is disabled when a plurality of switches are simultaneously closed to thereby prevent errors caused by multiple switch closures.

Abstract: A horizontally oriented curve is produced on a raster-type cathode-ray tube display by storing curve data words in a memory. The curve data word is representative of the height at which a dot is to be placed on the cathode-ray tube screen. The horizontal position of the dot is dictated by the position of the data word in the memory. The data words are read out of the memory in response to a horizontal address and the data words are compared to a vertical address. Where the data word is equal to the vertical address a dot is illuminated at a particular horizontal and vertical position. The curve is updated by writing a new data word into the memory and moving all of the existing data words one position in the memory. The data in the reconfigured memory is then displayed. Provision is also provided for filling in vertical gaps in the horizontal curve to provide a smooth curve.

Abstract: A central computer is utilized to control a recording medium while a peripheral computer is utilized to supply data to the recording medium for recording on magnetic tape. Method and apparatus is provided whereby an error indication is provided to the central computer if an error occurs in the transfer of data from the peripheral computer to the recording medium.

Abstract: The generation of a composite video waveform from three signals representing video data, blanking, and synchronization information is accomplished by supplying the video data, blanking and synchronization signals to the cathode side of three different diode circuits. The three different diode circuits are tied to a common voltage source on the anode side of the diode circuits. The forward voltage drop across the diode circuits determines the signal level seen by a video monitor in response to the video data, blanking and synchronization signals. In a preferred embodiment, at least one Schottky diode is utilized in each diode circuit to provide sharp edge definition for the composite video waveform. In a less preferred embodiment, conventional silicon switching diodes are used to replace the Schottky diodes but a sacrifice in edge definition for the composite video waveform results.