Abstract: A tunable capacitive coupling to a monopole antenna is provided which integrates the tuning mechanism into the supporting structure for the antenna. The base of the antenna is insulated from and supported by a cylindrical clamping assembly such as a metal compression ferrule in cooperation with an adjustment collar. This clamping mechanism enables the ferrule to be tightened like a drill bit in a chuck at any position along the base of the antenna. The coupling capacitance formed between the antenna radiator and the compression ferrule is proportional to the insertion depth of the antenna into the compression ferrule, thereby enabling the antenna to be tuned. The coupling method of the present invention enables repeatable tuning of the antenna either upward or downward in frequency within the band of frequencies accommodated by the particular antenna.

Abstract: In a multi-line telephone system, an improved method is provided for automatically detecting and indicating the status of each of a plurality of telephone lines despite variations in battery voltages on the line or lines and without requiring any adjustments by the user. Each of the lines in a system can be polled sequentially or individually as desired. The improved method measures the present voltage level associated with the selected line, distinguishes the condition of on-or-off hook or on-hold from other possible states, compares and processes the present measured voltage level in a state matrix, and updates the status indication of the selected telephone line accordingly. Status conditions which are detected and indicated by this method include on-hook, off-hook, and on-hold.

Abstract: A full duplex speakerphone for connection to a telephone system employs adaptive FIR filters for acoustic and electrical echo cancellation in a novel combination with analog gain controls responsive to incoming signal levels and a transmit level control responsive to the receive signal power level. The particular combination minimizes the amount of digital signal processing required to maintain full duplex operation by holding the signal dynamic range within predetermined limits.

Abstract: An overvoltage protection circuit for a CMOS electronic multimeter circuit uses a pair of complementary field-effect protection transistors connected to each input line of the meter circuit. The gate electrodes of the protection transistors are connected to bias voltage sources which provide bias voltages with magnitudes slightly less than the meter power supply voltages. The protection transistors go into conduction when an overvoltage condition causes the voltage on the input to exceed the bias voltages and the conducting protection transistors clamp the input voltage to substantially the bias voltage. Current caused by an overvoltage condition is shunted to ground thereby avoiding a charging condition in the power supplies.

Abstract: In accordance with the invention, a method for programing or editing, or both, the order of performance of digitally recorded information tracks, such as an audio recording, stored sequentially in an appropriate medium. The method allows a user to program or edit, via keystrokes, a program or sequence of tracks to be played. An apparatus for playing information tracks queued to be replayed in a predetermined sequence includes a key pad, which is used to enter commands and numeric information to establish a program queue, a display, which is used to display program events, and an interface processor, coupled to the key pad and the display, which is used to control the commands received from and sent to the key pad and to send display messages to the display. The apparatus also includes a control processor, coupled to the interface processor, which establishes from information stored on a medium in a sequential order, an ordered sequence of information tracks.

Abstract: A voice detection circuit uses normal and customary signal peaks and pauses in speech to distinguish voice from mere noise. The voice detection circuit includes an audio input device for receiving an audio signal and comparing it to a threshold, and a detector for generating the VOX output signal responsive to the presence of the peaks and pauses in the audio signal which rise above the threshold. The switch is actuated upon the VOX output signal indicating that the audio signal includes selected patterns of peaks and pauses and thus comprises voice signals. Illustratively, the threshold may be varied in accordance with the input signals when the voice detection circuit indicates that the input audio signals do not comprise voice signals.

Abstract: A method and apparatus for detecting diskette change is provided. A step pulse signal generated using the CPU is sent to the step pulse line of the disk drive, in addition to the normal step pulse signal which can be issued from the floppy disk controller. Thus, a step pulse can be issued directly by the CPU without using the FDC. By positioning the head in the outmost cylinder and issuing a step pulse, at a time when the direction signal indicates outward direction, the door-open status signal can be updated, without causing movement of the head. By preventing head movement in response to a step pulse, door-open status information is updated without undesirable effects of excessive head movement, drive spinning, head movement noise, constant illumination of the drive light or unnecessarily occupying the CPU or other components.

Abstract: A speaker amplification system incorporates an adaptable notch filter that can dynamically adapt to the frequency of feedback oscillations caused by acoustic feedback frequency in order to remove the feedback oscillation before they are amplified above an audible level. The adaptable notch filter is implemented as an adaptable finite impulse response filter by means of a digital signal processor. The finite impulse response filter also has an adaptable convergence factor which minimizes noise introduced by the filter. A special limiting routine is used to limit the values of the finite impulse response filter coefficients to prevent the filter from "blowing up" due to large input signal disturbances. The speaker amplification system also includes circuitry which provides multiple bands of equalization, with each band being capable of amplification.

Abstract: A coaxial connector plug and method for securing a coaxial cable in the plug without the need for crimping, trimming, or soldering the tip of the plug. A preformed solder, solder paste, or any type of conductive adhesive is deposited in the closed tip of a coaxial connector plug. The center conductive cable is then inserted into the adhesive material of the closed tip and heated to melt or cure the adhesive material, thereby establishing an electrical connection.

Abstract: The length (or the number of taps) of an adaptive finite impulse response (AFIR) filter is continuously modified to produce optimal echo cancellation. In accordance with one illustrative embodiment, this modification is performed by increasing or decreasing the number of delayed samples which are used to generate an echo estimate. More specifically, the number of samples used to generate the echo estimate is determined by selecting a trial number of samples and operating the filter for a sufficient length of time to allow the tap weights in the filter to stabilize. The tap weights are then examined to determine whether the taps at the end on the filter contribute at least a first threshold amount to the echo estimate. If not, the number of samples used in the filter is reduced and the process repeated. If the taps at the end of the filter contribute more than a second threshold amount, the number of samples is increased and the process is repeated.

Abstract: A system is disclosed which enables measurement of the elapse of a predetermined time period in a computer system by determining the speed of instruction cycle execution according to the number of instruction cycles occurring relative to system clock transitions. The result is a timing reference tailored for a specific function which is not intrusive of the system clock in the computer system, and is determined independently of the particular timing characteristics of the system. The elapsed time value corresponds to a function such as the time period for processing a data transfer command received by a CD-ROM drive. The system clock of the computer is used as a known timing reference and a software counter is incremented upon a transition in the system clock until the next transition in the system clock.

Abstract: A system for processing merchandise sale transactions for customers in a point of sale and warehouse facility. A main processor has a database for storing customer identification information and merchandise information and processes sale transaction records for customers. A point of sale system coupled to the processor has a controller and at least one pen-based computer in communication with the controller via RF transmissions. Program instructions respond to entry on the computer of a customer number and to entry of merchandise identification numbers to build a sale transaction record of selected items for purchase. The program instructions display item information and enable selection of items for addition to the sale transaction record, display delivery method instructions and enable their selection for addition to the sale transaction record, and transmit the transaction record to the processor to effectuate warehouse delivery of the selected items according to the selected delivery instructions.

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: A method and apparatus are provided for displaying graphical information concurrent with associated audio information within a multimedia computer system. The graphical information (CD+G) and the audio information, is read from a compact disk by a compact disk reader, and decoded by a digital signal processor. The graphical information is stored temporarily in a cache buffer within the compact disk reader and then transferred from the cache buffer to a host computer for display. While the compact disk reader plays the audio, the graphical information is transferred to the host computer for display within the multimedia system.

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 communications protocol for use in a main control processor used in an electronic product, which includes at least a second processor to control the user interface, such as a keyboard and a data display. The protocol gives the main control processor the ability to interpret commands received accurately and to disregard those commands that are erroneous. In addition, the protocol provides the user interface processor with all necessary feedback information it needs to determine its mode of operation or any possible error conditions that may have occurred. Furthermore, the protocol provides each processor the ability to utilize its own resources independently, while at the same time communicating with the coprocessor in a manner that treats the other processors as extended subsets of itself.

Abstract: The invention comprises a telephone answering device in which a microprocessor controller is coupled to all of the peripheral components through a single common multi-bit data/instruction bus and each peripheral component is coupled to the data bus through a latch which is enabled responsive to an enable instruction placed on a port of the controller.

Abstract: A digital multimeter includes a microprocessor control and a keyboard input. The microprocessor functions to control the display of parameters measured by the meter and displays such measured parameters. The keyboard includes switches to allow the user to select a parameter which is desired to be measured as well as a range of values for that parameter for use in measuring parameters of a device under test connected to the multimeter. The microprocessor communicates with the keyboard and functions to control a resistor and switch network to configure the multimeter to test selected parameters within selected ranges. The multimeter incorporates an overload protection function which compensates for an over-large voltage on the input leads of the multimeter, thus preventing damage to the circuit and to the multimeter.

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.