Abstract: An oscillation circuit for a radio receiver system. The oscillator circuit includes a tank circuit, a first and second transistor, and a first and second low pass filter. The first transistor forms a first current loop when the first transistor is active. Similarly, the second transistor forms a second current loop when the second transistor is active. The first low pass filter is connected in an electrical series connection within the first current loop and the second low pass filter is connected in an electrical series connection within the second current loop. As such, the first and second low pass filter serve to reduce the gain of the oscillator circuit below a secondary resonant frequency of the tank circuit to prevent an oscillation condition, thereby preventing unwanted oscillations at a secondary resonant frequency.

Abstract: An intelligent power switching system for controlling the electrical connection of a power source to each of a plurality of outputs, such as personal computer components or electronic entertainment equipment. Switch circuitry is coupled to relay circuitry for generating signals responsive to user commands to select an "on" or "off" state with respect to each output. A processor receives switching signals and generates control signals to effect actuation of the relays. Responsive to user programming commands, the processor stores the switching signals, their sequence and the time delay between their generation. Responsive to a subsequent abbreviated user "power-on" command, the processor generates control signals by reading the stored switching signals, their sequence and time delay, and automatically actuates the relays with respect to each output in the same order and with the same time delay as defined by the user programming commands.

Abstract: An automatic transistor checking method is provided, whereby an unknown, bipolar transistor may be typed, pinned and checked for forward DC gain, H.sub.fe. The method is suitable for portable instruments, because the method uses little battery current to perform the H.sub.fe measurement. The method automatically determines transistor type (NPN or PNP) and pinout, making it suitable for quick checking of batches of unknown devices.

Abstract: A relatively large protection resistor is connected between the measurement in-out terminal and the internal circuitry of a digital multimeter. A clamping circuit at the input to the internal circuitry insures that any voltage applied to the input terminal will be dropped across the protection resistor, thereby avoiding an over-voltage condition which could damage the internal circuitry. A resistive divider network used to make measurements is connected between the protection resistor and the clamping circuit and is designed to take the protection resistor into account during measurements.

Abstract: An automatic transistor checking method is provided, whereby an unknown, bipolar transistor may be typed, pinned and checked for forward DC gain, H.sub.fe. The method is suitable for portable instruments, because the method uses little battery current to perform the H.sub.fe measurement. The method automatically determines transistor type (NPN or PNP) and pinout, making it suitable for quick checking of batches of unknown devices.

Abstract: A bandpass filter suitable for use in modem circuitry and other applications which require the filter's center frequency to be switched is disclosed. The filter circuit has the characteristic that although the center frequency is changed the overall gain of the filter remains constant. This characteristic results from using a plurality of filter sections which each have low individual gain and providing compensating gain at the input of the filter. In addition, compensating gain elements are used in each filter section so that when the center frequency of the filter is changed, the gain of each filter stage remains constant.

Abstract: Electronic circuitry for generation of graphics images on a computer display screen is disclosed which allows graphics capability to be added or retrofitted to computers having standard video display character generation circuitry. The graphics circuitry receives address, data and control signals from the normal computer peripheral bus. Address signals received by the graphics circuitry are interpreted as command signals and, in accordance with the command signals, data present on the computer peripheral data bus is interpreted either as graphics data to be written in a random access graphics memory or as an address location for such data in the memory. The graphics circuitry normally operates asynchronously with respect to the computer under control of the character clock generated by the character generation circuitry.

Abstract: A bandpass filter suitable for use in modem circuitry and other applications which require the filter's center frequency to be switched is disclosed. The filter circuit has the characteristic that although the center frequency is changed the overall gain of the filter remains constant. This characteristic results from using a plurality of filter sections which each have low individual gain and providing compensating gain at the input of the filter. In addition, compensating gain elements are used in each filter section so that when the center frequency of the filter is changed, the gain of each filter stage remains constant.