Abstract: An ac mains test apparatus and method. An audio frequency signal measurement instrument is provided with a circuit for testing the ac mains to which the instrument is connected. The ac mains is internally connected to a coupler which presents an attenuated portion of the ac mains to the low level input of the instrument. A switch is provided for selectively connecting the input either to an audio signal to be measured or to the ac mains portion. The coupler both attenuates the ac mains for input to the instrument and isolates the relatively high ac mains voltage from the low level input.

Abstract: A device for displaying information by a hand which is driven by a stepping motor in both forward and backward directions and which moves within a limited range, in which the stepping motor receives a driving signal enough to move and scan the hand in one direction in the whole range of the limited region for facilitating the attachment of the hand, and depending on the object to be measured, overtravel inhibiting circuit means are added to prevent any misdisplay.

Abstract: A high input impedance AC buffer for use in an instrument that does not require high frequency compensation or calibration. An op-amp receives an input signal that is to be measured via a high resistance input resistor and produces an output signal proportional to the input signal. A feedback resistor block and a feedback attenuator form the feedback path of the buffer and establish buffer gain. The low resistances of the feedback block and the feedback attenuator are substantially less than the resistance of the high resistance input resistor, precluding the need for compensation and calibration capacitors. A switching circuit operates to select resistors in the feedback resistance block and the feedback attenuator to provide predetermined gains for the buffer.

Abstract: An automatic range selection-type analog tester capable of automatically switching to the optimum measuring range even if the measurand of an object to be measured is undetermined. A range select signal generating circuit is designed to generate a range select signal for selecting one of a plurality of voltage dividers of a range selector circuit in such a manner that the divided voltage output of the object divided through the range selector circuit comes into a predetermined range and also a range display displays the corresponding measuring range in accordance with the range select signal.

Abstract: A method for measuring at least one electrical parameter of the operation of a p-phase power line, p being a positive integer, arranges respective sensing apparatus to sense at least one of the voltages and currents associated with each phase of the power line. Analog-to-digital conversion apparatus is used to digitize the response of each sensing apparatus, thereby to generate corresponding digital responses. A digital computer is used to correct each digitized response of the analog-to-digital conversion apparatus for non-linearities, gain errors and phasing errors in the responses of the sensing apparatus and for non-linearities and gain errors in the responses of the analog-to-digital conversion apparatus. The computer is used to high-pass digitally filter each digital response that has been corrected, in order to suppress any attendant direct term.

Abstract: A signal probe apparatus having a probe tip, a grounding attachment, a main body portion and a connector for use with a signal measuring device. The probe tip and the grounding attachment are coupled by way of first and second signal lines to the connector for supplying signals therefrom to the signal measuring device. A plurality of circuit elements, such as resistors, are connected between the second signal line and a third line in the connector; and switch means located on the main body portion enables a predetermined circuit value, for example, the resistance between the second and third lines, to be selectively changed to a respective value which corresponds to a respective one of several predetermined functions which may be performed by the signal measuring device. The selected circuit value is detected by the signal measuring device and the corresponding function is thereafter implemented.

Abstract: A measuring device comprises a plurality of signal converters, for measuring a signal by different measuring methods, and a selector, for selectively activating one of the signal converters. A control signal is developed in accordance with the activated signal converter. The measured value of the signal is exhibited in a color which is controlled by the control signal, to indicate the selected measuring method.

Abstract: In multimeters for the selective measurement of different measurable variables having test signals that are detected by the multimeter through the use of various input circuits assigned to respective measurable variables, an input circuit can be connected which is not suitable for an input variable set at a measurement range switch. In order to draw the attention of the operator at least to an error that the operator is responsible for, at least one auxiliary circuit is provided and fed through the measurement range switch in such a manner that a fixed assignment to a particular input circuit and consequently to a particular measurable variable results. The assignment is dependent on a switch position. Inserted in the auxiliary circuit is at least one function generator which triggers a function or a combination of a plurality of functions upon actuation, which is preferably achieved by closing the auxiliary circuit. This counteracts the operating error in switching the measurable variable.

Abstract: A salt analyzer is disclosed capable of measuring the conductivity of a saline solution when either contact or non-contact probes are used. In particular, the salt analyzer employs circuitry capable of switchably measuring the various electrical parameters necessary for determining the conductivity of a solution when either contact or non contact probes are used.

Abstract: A wide power range radiation monitor includes a pair of diodes with their cathodes interconnected and with an additional capacitor coupled in parallel to one of the diodes. The detector of the radiation monitor provides two outputs, a low power output and a high power output, which outputs are connected to the anodes of the detector diodes. The arrangement of dual diodes and capacitance provide the diode detector of the monitor with a greater than 40 dB square law region.

Abstract: An electronic watthour meter is digitally configurable to operate as several different types of watthour meters for metering electrical energy from a variety of different electric utility services. Automatic scaling of line input currents is provided to scale the voltage input to an analog to digital converter over selected ranges such that low level and high level input signals are measured in an optimum range. A digital signal processor is employed to calculate values for metered electrical energy and output pulses, each proportional to a quantum of energy flowing in the circuit being metered. The processor calculates the value of DC offset errors inherent in the various analog circuits of the meter and uses that value in the calculation of metered electrical energy to compensate for such offset errors. The meter employs automatic and manually initiated test functions for testing the operation of the processor and other critical circuits in the meter.

Abstract: A method for measuring various measurable variables with a multimeter includes specifying one of a plurality of measurable variables to be determined through a position of a measurement range switch and/or through a selection between various input connections respectively assigned to the measurable variables. Input circuits are assigned to respective measurable variables. A preliminary test is performed for at least one of the measurable variables to check if an input circuit is suitable for picking up an applied test signal, before an actual main measurement is carried out. A given input circuit is enabled for picking up the test signal only if the preliminary test has shown that the test signal is suitable for the given input circuit. An error signal is issued if a test signal being unsuitable for the given input circuit ensues. A multimeter for measuring various measurable variables includes a measurement range switch and/or various input connections for specifying a measurable variable to be picked up.

Abstract: The invention discloses a magnetic field radiation monitor which comprises at least one sense coil adapted to sense magnetic flux from the electromagnetic field to be measured for both ELF and VLF type of fields. The sense coil is coupled to a detection circuit wherein an EMF generated in the sense coil will be amplified and frequency compensated in the circuit to give an extremely flat frequency response allowing accurate detection of complex magnetic fields. The circuit consists of an ELF and VLF stage, both selectively coupled to the sense coil and incorporated into the circuit by a user activated switch. The output of either the ELF or VLF stages is further processed and the output is provided to a display to indicate the magnetic field strength measured. The magnetic field radiation monitor may be calibrated to yield a true RMS measuring platform using a RMS detector circuit which will give an accurate indication of magnetic energy content for complex waveforms.

Abstract: A voltage measuring instrument which generally includes signal conditioning circuitry coupled to input probes for protection against overvoltages and processing of input voltage signals. A VAC/VDC control circuit will determine whether AC or DC voltages are present, and will positively indicate when no voltage is present in a test circuit. The metering circuit of the invention will thereby automatically determine the proper mode of operation for the type of voltage present in a test circuit so as to eliminate user selection of operating parameters and possible errors. Further, the metering circuit is adapted to generate a proper reference voltage for the measured voltage automatically, to again eliminate selection of a voltage range by the user. A power supervision circuit is adapted to automatically shut off the measuring instrument after a predetermined amount of time has elapsed, and will automatically shut off power in the event that available battery power drops below a given level.

Abstract: An R/Z converter for use with a conventional digital multimeter (DMM) provides enhanced capabilities of the DMM in measuring impedance and other functions where DC measurements are undesirable. The R/Z converter converts the test voltage of a conventional DMM into a square wave that is applied to the device being tested. The voltage from the tested device is seen by the DMM as an average DC value that is proportional to the impedance of the device.

Abstract: An input protecting mechanism for a measuring device, such as a digital multi-meter, wherein a shutter is provided to open and close selectively input terminal holes for leads, depending on the particular measuring function selected so that the test lead cannot be placed in an improper terminal, so that advantageously, damage to the internal circuitry is prevented by preventing erroneous signals from being applied to the wrong circuits.

Abstract: A system for simultaneously probing an electrical test circuit while remotely controlling the test equipment used to measure the probing. The probing is performed by the use of an electrical test probe of the type utilized with oscilloscopes or the like. Incorporated within the probe are switches adapted to detecting both lateral and longitudinal pressures exerted by the probe user. The lateral pressure is applied to the lower portion of the probe and depending upon the direction of the pressure causes a cursor displayed on the test equipment to move. The user moves the displayed cursor to the desired position, which position corresponds to a function or option of the test instrument. Upon selection, the user exerts a longitudinal force upon the probe, which force is detected by the probe and activates the selected function or option on the test instrument.

Abstract: It is known to provide measuring instruments, such as oscilloscopes or other measuring instruments, with analog adjustment elements for adjusting various parameters, such as the horizontal and vertical position of a signal (s1, s2) to be displayed, of trigger devices, etc. A digital measuring instrument is disclosed having digital adjustment elements in which the reaction behaviour of the parameters to be set substantially corresponds to that of a measuring instrument with analog adjustment elements. For this purpose, the adjustment elements are constructed as rotatable pulse generators and the measuring instrument is provided with a pulse processing device by which the pulse duration (T, T') of the pulses generators is determined. Thus independently of the rotational speed, a parameter reaction behaviour can be set by this device which results in a natural reaction behavior similar to that of analog adjustment elements.

Abstract: A multi-function, multi-mode switch for an instrument that changes the instrument between primary and secondary functions and between first and second modes of operation within the primary and secondary functions. The instrument changes from the first mode of operation to the second mode of operation when the switch is actuated for a first period of time. The instrument changes from the second mode of operation to the first mode of operation when the switch is activated for a second period of time. The instrument changes between the primary and secondary functions when the switch is operated for a third period of time. The switch controls a program that instructs the instrument to perform the appropriate operations. The program also instructs the instrument to confirm that an operation has occurred via audible and visual feedback.

Abstract: A solid state speed indicator for railroad locomotives is provided with a plurality of indications in addition to speed. These include an acceleration indicator and an overspeed indicator. In addition, the speed indicator is provided with a dual range speed function having at least one particular use in drag operations. A variation of the solid state speed indicator is a retrofit design that replaces the meter movement in existing speed indicator equipment with a solid state display.

Abstract: In multimeters having a plurality of input connections there is a danger of the measuring conductors being incorrectly connected in such a manner that the setting of the measurement range switch does not correspond to the input connections to which contact is made. In order to avoid damage which may be caused by making an incorrect contact to the input connections, an electrically and/or mechanically acting disabling device is coupled to the measurement range switch for permitting a disabling of particular input connections. The disabling is carried out in such a manner that contact can always only be made to that input connection for receiving a test signal through the measuring conductors, to which a measurable variable is assigned that corresponds to the measurable variable set with the measurement range switch.

Abstract: A multipower type electronic system discriminates the kind of power source connected to it. A detection voltage and/or a detection voltage timing interval is set on the basis of the discriminated type of power source and a predetermined display is executed on the basis of the power source type discrimination and/or the detection voltage setting.

Abstract: A modular metering instrument including one of a plurality of sensing probes or probe modules including identification and calibration information stored therein and a meter module which can identify the sensing probe when the sensing probe is connected thereto. The storage of calibration and identification information in the sensing probe allows the meter module to be utilized with any one of a number of sensing probes to sense different physical parameters. The sensing probe includes at least one sensor and related circuitry to generate a signal relating to the sensed parameter. The meter module analyzes and calibrates the signal and displays the measured parameter.

Abstract: A display transducer adapter for obtaining and displaying power system information from a protective relay. The information includes watt, voltage, current, reactive power, and fault location information. The information may be converted from a digitized format into analog signals and those signals may be provided as outputs, the functions of which are user selectable. The user may also selectively scale the outputs to cover a specified range.

Abstract: A very fast autoscale feature can be implemented in a digitizing oscilloscope by using dedicated peak detector hardward [14] capable of operating at the maximum sampling rate of the A/D converter [12] to determine the minimum and maximum values of said input signal, in combination with a trigger counter [24, 26] to count the number of trigger events in the analog input signal. While in the autoscale mode, the oscilloscope microprocessor [22] can then set the appropriate scale and offset for the Y-axis of the display as a function of the maximum and minimum values determined by the peak detector [14] and set the sweep rate as a function of the count provided by the tripper counter [26].

Abstract: A test lead socket indicating device is used for a volt-ohm-milliammeter (VOM) having a select input which is operable to set the VOM in a voltage, current or resistance measuring mode, a common input socket, a voltage socket, a resistance socket and a current socket. The test lead socket indicating device includes an indicator unit provided on the VOM and having a voltage indicator lamp disposed adjacent to the voltage socket, a current indicator lamp disposed adjacent to the current socket and a resistance indicator lamp disposed adjacent to the resistance socket. A counter unit has an input terminal connected to the select input. The counter unit has a digital signal output which is incremented each time the select input is operated. A decoder unit receives the digital signal output from the counter unit. The decoder unit activates one of the voltage, current and resistance indicator lamps according to the digital signal output.

Abstract: A single-phase multi-ratio current transformer, having at least two different current ratio or output levels through the appropriate wiring of its output leads without any intervention of the main current circuit of the system, having a primary current conductor, a secondary circuit having at least two change-over output wires S.sub.2 and S.sub.3, respectively connected to two contacts and a main output terminal connected to a common contact. A plurality of corresponding plug-in configurational devices, each have at least one jumper wire positioned to the common contact to only one of the two contacts, in order to give the current transformer the current ratio or output level corresponding to the selected wire S.sub.2 or S.sub.

Abstract: A meter (10) for measuring extremely-low-frequency radiation includes a coil circuit (22) whose output is filtered by a sharp-cut-off high-pass filter (24) to pass standard house-current frequencies but suppress the frequency components that would predominate as a result of movement of the meter with respect to the earth's magnetic field. An integrator (26) compensates for the frequency response of the coil circuit (22), an RMS circuit (35) converts the signal to its root-mean-square value, and a display circuit (28) provides a display determined by the resultant signal.

Abstract: The present invention relates to a measurement circuit for providing the digital value of an analog electrical signal. The digital measurement circuit for measuring an analog electrical signal produces a measurement signal (M) and includes an amplifier (1) which receives said electrical signal (I), followed by an analog-to-digital converter (2) which delivers digital data (N). The gain of the amplifier (1) is controlled by a control signal (C) and said gain can take up at least two values. The measurement circuit further includes a control unit (3) producing said control signal (C) and storing the digital data corresponding to different gain values, and includes means for producing the measurement signal (M) on the basis of said digital data (N).

Abstract: A multi-mode signal measurement system provides at least True RMS and Average RMS signal measurement modes in one system in response to a measurement mode selection made by an operator. The system controls the processing of the input signal by a selected signal measurement unit according to the operator selected signal measurement mode. After signal processing is complete, a display unit displays a value of the measurement of the input signal according to the selected measurement mode. Other measurement modes providing peak value and resistance measurement readings may also be provided.

Abstract: A range selecting impedance is switched into or out of a parallel range-selecting network by connecting the impedance across the network through an n-channel and a p-channel FET connected in parallel output configuration. The n-channel FET does the switching if the drains are negative with respect to the sources. The p-channel FET does the switching if the drains are positive with respect to the sources. Each FET is controlled by a gate drive whose output waveform is varied to select the rate at which the FETs switch. In cases of several different switched range impedances, the FETs are used to switch the smallest impedance into the network, another range impedance is selected, and then the FETs used to switch the smallest impedance out of the network. In this way, fast glitch-free range switching is achieved.

Abstract: A digital multimeter having automatic function selection capability includes a signal type detector and an analog-to-digital converter formed as an application specific integrated circuit. The signal type detector has a comparator circuit that compares the analog input signal to be measured with predetermined thresholds and stores the resulting values, which are related to the type of analog input signal, in a memory that is also a part of the signal type detector. A controller executes an automatic function selection program that causes the controller to read the stored values and generate a corresponding function code, which causes an analog-to-digital converter to be configured to perform an appropriate conversion function on the analog input signal. When a change in the type of analog input signal is sensed, the controller aborts the present measurement cycle and proceeds with a next measurement cycle in which the changed analog input signal is measured.

Abstract: A method for examining an input signal and setting a modulation domain measuring instrument to a state which will produce a measurement and a stable, centered, properly scaled display of the signal, automatically. After finding the 50 percent voltage threshold of the input signal, an iterative process determines the minimum and maximum input frequency, then checks the ratio of these two frequencies against instruments limits, and adjusts the display values, if necessary to show only the higher frequencies. The method then varies the measurement parameters to seek the best frequency resolution while maintaining the measurement and display of frequency modulation. The display frequency scale is set to display the signal in the center half of the display, using values with no more than two significant digits for the center and span. The time scale is set to display a selected number of modulation cycles.

Abstract: Disclosed is a pulse counting circuit for counting pulse signals comprising a first pulse signal generating means for generating a first pulse signal corresponding to an input signal, a counting means for counting at least either of said first pulse signal and a second pulse signal which differ from said first pulse signal corresponding to said input signal, said first pulse signal possessing a pitch set smaller than that of said second pulse signal, and a control means for selectively controlling the operation of said count means for counting said first and second pulse signal.

Abstract: A multimeter with variable color digital display indicates measured values in a digital format and in a variable color. The multimeter includes a color control circuit for controlling the color of the digital display in accordance with the measurement quantity, method, unit, mode, function, range, location, modifier, control, limits, and the like. A color converter circuit is disclosed for converting analog voltage to variable color.

Abstract: Disclosed is a digital multimeter having an automatic function selection capability. The device includes a sensing circuit connected to its input to respond to the type of analog signal which is sensed and to provide logic signals which are characteristic thereof. These logic signals may be utilized to cause generation of encoding signals to encode and dispose the converter circuit to perform the desired conversion function and provide the desired display as a function of the analog input. The device may include an internal reference signal source such as a DC reference potential and the sensing circuit may sense a differential between such reference source and the external analog signal to make a determination to utilize or disconnect the reference signal source in performing the function dictated by the nature of the analog signal.

Abstract: A signal detector includes a signal input section, a detector, and a converter. The signal input section inputs a high frequency signal to be measured. The detector detects the high frequency signal to be measured input by the signal input section. The converter amplifies the output from the detector and includes a variable gain preamplifier which has a first gain higher than a linear gain when the detecting output is smaller than a predetermined value and a second gain lower than the linear gain when the detecting output is larger than the predetermined value. A cable line transmits an output from the variable gain preamplifier of the converter of the signal detector. A measuring equipment body includes a decoder and an analyzer.

Abstract: A scale is disclosed for a measuring instrument in which a plurality of display elements, specifically liquid crystal display elements which are energizable to a visible condition or an enhanced visible condition selectively to provide a linear scale or a logarithmic scale. The scale is divided into decades which specifically have twelve display elements of which ten are selectively energizable to provide the linear scale and then to provide the logarithmic scale.

Abstract: An apparatus for simulating a multimode meter having a pair of test leads, a function switch, and a range select switch is provided. The simulated multimeter apparatus is fed by digital display data signals and provides a numeric display representative of a number corresponding to digital data display signals. Further, the simulated multimeter apparatus is fed by a plurality of switch signals which correspond to predetermined locations of the function and range select switches and fed by an input data stream corresponding to simulated electrical parameter values, related to the values of the functions switch and the range switch, for converting the input data stream into the digital display data signals.

Abstract: A single integrated circuit operable in either a single chip mode or a host dependent mode.

Abstract: An electronic watthour meter is digitally configurable to operate as several different types of watthour meters for metering electrical energy from a variety of different electric utility services. Automatic scaling of line input currents is provided to scale the voltage input to an analog to digital converter over selected ranges such that low level and high level input signals are measured in an optimum range. A digital signal processor is employed to calculate values for metered electrical energy and output pulses, each proportional to a quantum of energy flowing in the circuit being metered. The processor calculates the value of DC offset errors inherent in the various analog circuits of the meter and uses that value in the calculation of metered electrical energy to compensate for such offset errors. The meter employs automatic and manually initiated test functions for testing the operation of the processor and other critical circuits in the meter.

Abstract: A measuring device includes a variable color display for indicating measured values of an input signal. A comparator and a color control circuit are provided for controlling the color of the display in accordance with the relation of the measured value of the signal to predetermined limits.

Abstract: There is disclosed an input condition sensing circuit for use in a facility management system which is selectively operable in a first mode for sensing the presence or absence of a voltage potential or a second mode for sensing a high or low impedance and which provides a binary output signal indicative of the condition being sensed and an amplifier coupled to the input for generating a control signal having an amplitude relating to the input condition being sensed. The circuit also includes detecting means coupled to the amplifier for providing a binary output in response to the control signal and indicative of the condition being sensed and select means coupled to the detecting means for selectively conditioning the circuit for operating in either the first or second mode.

Abstract: A calibrator supplying electric parameters (viz voltage, current and resistances) over plural ranges to a meter to be calibrated comprises internal components for deriving each parameter over the plural ranges, an internal voltage reference, a DAC, a memory, an analog comparator and analog-to-digital converter. The internal components are connected in circuit with the internal voltage reference, analog-to-digital converter, comparator and memory for writing data signals into the memory indicative of calibration correction factors for the internal components. The internal components are connected in circuit with the memory and DAC so the DAC responds to the stored data signals indicative of the calibration correction factors to enable the value of the parameter supplied to the device by the internal components to be modified and corrected in accordance with the calibration correction for the parameter.

Abstract: Adjustable electronic graticules for measuring waveform distortions are generated from operator inputs indicating a measurement mode and a scale factor. A template of a graticule for the measurement mode in the form of a display list of move and draw instructions is scaled by the scale factor and a measurement value is computed from the scale factor and the instrument units per division setup. The graticule and measurement value are stored as a modified display list. A readout engine interprets the modified display list and produces electrical signals for drawing the graticule and measurement value on a display monitor. The electrical signals are combined with the waveform for display on the display monitor. The operator varies the scale factor until the displayed graticule touches the waveform at a measurement point, and the measurement value is accordingly displayed.

Abstract: A measuring device includes a display which is comprised of a plurality of adjacent display elements, each including a display area for exhibiting an indication of the measured value, substantially surrounded by a variable color background area. The color control inputs of the background areas, which are respectively coupled, may be selectively activated for illuminating the background areas in a uniform color which effectively indicates that it relates to the indication of the measured value exhibited on the display areas.

Abstract: A potentiometer used with a voltmeter has an impedance transformer to which a voltage to be measured is applied, a bank of resistors acting collectively as a variable resistor and having switches connected in parallel across the respective resistors of the bank, a switch control circuit, and a multiplier-setting circuit, all connected in series. The resistors have resistances r, 2r, 4r, 8r, . . . , 2.sup.n-1 r or 10.sup.0 (r, 2r, 4r, 8r), 10.sup.1 (r, 2r, 4r, 8r), . . . , 10.sup.n-1 (r, 2r, 4r, 8r), where r is a minimum, or unit, resistance value. The unit resistance value r multiplied by a multiplier N of two or more digits is equal to the resistance value of the variable resistor bank.

Abstract: An ion chamber type instrument for measuring radioactivity includes a high gain operational amplifier having a feedback network of range determining resistors connected between the amplifier output and input. Electronic switches in series with at least some of the range determining resistors function as range selector switches for the measuring instrument. Each switch includes two series-connected transistors and a third transistor, the interconnection point between the two series-connected transistors being connected to the electrical neutral point of a measuring circuit via the third transistor. Each switch, when in an "off" or non-conducting condition, provides a high effective resistance of, for example, 1.times.10.sup.15 ohms so as to minimize errors caused by leakage current fed back into the input of the high gain operational amplifier.

Abstract: An adaptive data acquisition multiplexing system having a monitor terminal and one or more remote terminals with a communication link between them. The remote terminals each include signal conditioning for a plurality of sensors. Upon commands from the monitor terminal, signals providing the remote terminals' current configuration and status, and instructions for changing the remote terminal configuration, are transmitted from each remote terminal to the monitor terminal. Menu driven prompts at the monitor terminal permit commands to be transmitted from the monitor terminal to the remote terminals, selectively altering the configuration of any remote terminal to enable it to acquire and transmit data, as well as its configuration and status information, in the desired format. Alterations in any remote terminal's configuration can then be verified at the monitor terminal.

Abstract: A device for displaying the value of a quantity represented by input data comprises a mobile indicator member (24) driven by a stepping motor (20), a control circuit (18) for this motor for delivering drive pulses to the motor in response to the input data to move the indicator member to a position corresponding to the value of the quantity, and a dial (26) for showing an indexing system, for example a scale, which cooperates with the indicator member to indicate the value at least approximately. The dial comprises a liquid crystal, electrochromic or electroluminescent electrooptical display device (26) which displays the indexing system in response to signals from another control circuit (28) when the latter receives an activation signal. The device enables values of a single quantity situated in different ranges or values of distinct quantities to be indicated, by making the cell selectively display corresponding indexing systems. A specific application of the device is for automobile dashboards.