Abstract: Disclosed is a fully digital spectrum analyzer which includes a digital frequency translator that makes it possible to effectively analyze frequency bands that do not start at zero frequency. With the translator, the available spectral lines can be within the band of interest and not wasted in the range from zero frequency to the start of the band, and as a result the band is examined at optimal resolution. The translation takes place after the signal to be analyzed has been digitized, and the translator time-shares much of the conventional circuitry of the spectrum analyzer, to thereby minimize the cost of translation. Additionally, the spectrum analyzer includes an analog network that reduces the frequency of very fast signals so they can be analyzed by a spectrum analyzer having a relatively low upper frequency limit.

Abstract: A combination display window cover, tilt stand, and handle for a portable instrument, the unit serving each of these functions by virtue of an integrally formed appropriately shaped unit which can preferably be molded as a single piece of elastomeric material and does not introduce any substantial cost increase over and above a conventional handle. The invention is suited for use in conjunction with a portable instrument which includes a housing of generally parallelepiped configuration having relatively large area front and rear opposing surfaces and relatively small area top, bottom and opposing side surfaces, the housing having a display window extending across its front surface relatively near the top edge thereof and substantially parallel to the top edge.

Abstract: The analogue storage circuit includes a charge transfer device such as a charge-coupled device (CCD) and a quantizing circuit. The charge transfer device is arranged to shift an analogue signal from its input to its output, the analogue signal being subject to a change in magnitude during such shifting.The quantizing circuit receives the analogue signal from the output of the charge transfer device and quantizes that signal at a respective one of several substantially discrete levels. The quantizing circuit is arranged to apply the quantized analogue signal to the input of the charge transfer device, whereby in operation the analogue signal is circulated round the loop defined by the charge transfer device and the quantizing circuit. The quantizing circuit is further arranged to quantize the analogue signal, upon each subsequent receipt thereof, at the same one of the discrete levels.

Abstract: A radiation gauge for measuring the profile of a moving strip, e.g. strip issuing from a strip rolling mill, comprises two X-ray tubes arranged on one side of the strip. The X-ray tubes are connected in push-pull configuration, for pulsing in alternation, and they each produce a respective curtain of radiation which intersects the strip in a respective straight line extending across the width of the strip, perpendicular to its direction of travel: these two straight lines are aligned with each other and overlap slightly in the center of the strip. A linear array of radiation detectors is disposed on the other side of the strip, so as to receive the radiation which passes through the strip. Signal processing circuitry processes the detector output signals to display the deviation of the thickness profile of the strip from a predetermined thickness profile.

Abstract: A phase-locked demodulator for demodulating a phase-difference modulated carrier having a repeated phase offset increment introduced therein. The demodulator includes, in common with conventional phase locked demodulators, a mixer having a first input connected to receive the modulated carrier and a reference carrier generator such as a voltage controlled oscillator (VCO) connected in a phase-locked feedback loop forming the second input to the mixer. In order to reduce the number of output levels, the VCO is tuned to a frequency Fr=Fc.+-.Fb[(.alpha.)/360] where Fc is the carrier frequency, Fb is the baud rate and .alpha. is the repeated phase offset. In this way the phase offset increment introduced into the modulated carrier is substantially cancelled out thereby leaving only the phase changes containing data information.

Abstract: A circuit for protecting speakers connected to the output of an audio amplifier. The output of the amplifier is connected to a filter which blocks normal audio frequency signals but passes both high and low frequency signals outside the normal audio range. The positive and negative filter output signals are connected respectively to the inverting and non-inverting inputs of an operational amplifier whose output is connected via a turn-on delay circuit to a speaker relay, which, when closed, connects the speaker to the amplifier. The turn-on delay circuit prevents speaker relay closure until turn-on transients have ended. If a DC voltage or a high frequency signal is present at the amplifier output, the operational amplifier generates a signal to open the relay thereby disconnecting the speaker from the amplifier output. The speaker relay quickly opens when power is turned off so that amplifier turn-off transients are not connected to the speaker either.

Abstract: The data terminal is manually operable and is intended for communicating with a data processor. The terminal has a keyboard having a plurality of manually selectable keys, each of which represents a respective message to be communicated to the processor. A display is provided having a plurality of zones each corresponding to a respective key of the keyboard, and the display is arranged to display in each zone an indication of the message represented by the key corresponding to that zone. The keys are in the form of touch keys. Merely touching a key serves to manually select that key, and causes the visual appearance of the display to change, so as to indicate which key is selected. This change may for example be a reversal of the relative brightness of the corresponding zone of the display e.g. dark on light instead of light on dark. Actually depressing the key, as opposed to just touching it, produces an output signal for communicating the message represented by the selected key to the processor.

Abstract: A moving coil instrument with a unique base of nonmagnetic sheet metal construction so arranged that sides of the base can flex to receive and clampingly retain a magnetic circuit, without causing movement of end portions of the base which support the moving coil for pivotal movement. Projections of a casing cooperate with circular mounting ears on the sides of the base to exert an inward force to assist the clamping action of the sides to securely hold the magnetic circuit against movement. A unique unitary sheet metal balance cross and a terminal plate assembly provide for connecting inner ends of taut bands which support the coil for movement. Cooperating tabs and slots on the coil, balance cross, and terminal assembly provide for securing the terminal plate and balance cross at opposite ends of the coil in predetermined locations with respect to the coil.

Abstract: A speed-controlling circuit for controlling the rotational speed of a D.C. electric motor in which the electric current is supplied to the D.C. motor through a switching circuit which is periodically open for a predetermined fixed time interval. The switching circuit is controlled by electrical pulses having a repetition rate which varies in dependence upon the rotational speed of the motor, whereby to periodically interrupt the supply of current to the motor.

Abstract: A density transducer employs a hollow cylinder capable of vibrating in the circumferential (or hoop) mode as the density sensing element, the cylinder being open at both ends and arranged so that the fluid whose density is to be transduced can come into contact with only the internal surface of the cylinder. The opposite ends of the cylinder are each secured to a respective clamping ring, which establishes a node at its respective end of the cylinder. The clamping rings each have a piston face which faces axially away from the cylinder and is acted on by the pressure of the fluid, thereby applying a compressive axial force to the cylinder which tends to reduce the effect of variations in the pressure of the fluid on the frequency of the vibration.

Abstract: A rectifying circuit comprises a high gain A.C. amplifier having first and second rectifying means connected in respective negative feedback paths between its output and its input and arranged to pass respective feedback currents of opposite polarity. A current copying device is responsive to the current flowing in one of the rectifying means to copy this current.In a preferred embodiment, said one rectifying means comprises the base-emitter junction of a first transistor, whose collector is connected to the input of the amplifier, and the current copying means comprises a second transistor, matched with the first transistor, and having its base-emitter junction connected in parallel with the base-emitter junction of the first transistor. The rectified output signal in this embodiment is taken from the free collector of the second transistor.

Abstract: A flowmeter comprises an axial flow measurement turbine having a relatively thin turbine disc secured to a shaft which is supported on at least one axial bearing. At high flow rates, it is possible for a large pressure differential to build up between the opposite axial sides of the disc, subjecting the turbine to an axial force which results in excessive friction at the bearing and therefore reduced life and reduced accuracy. To solve this problem, the disc is provided with apertures passing axially therethrough, and a set of blades is secured to the upstream face of the disc to force fluid to flow through these apertures, and thus substantially eliminate the pressure differential.

Abstract: A hub lighted indicator suitable for aircraft applications including one or more pointers, each capable of a full 360.degree. excursion over the dial face. The pointers include a portion which extends through a central circular aperture in the dial between the dial and the hub lighting member and are connected in a non-interfering manner to corresponding ring gears mounted for rotation coaxially with the dial aperture. The ring gears are driven in accordance with the quantities being measured to cause a corresponding excursion over the dial face of the connected pointer. Electrical connections are made to the hub lighting member from the rear portion of the indicator through the center portions of the ring gears.

Abstract: A panel meter having a unique casing with an adapter on the casing. The meter movement is in a compartment of the casing and the adapter is secured to the casing and cooperates with the casing to define a compartment separate from the meter compartment. Components such as calibrating resistors and rectifiers can be installed, if required, in the separate compartment after the meter movement is installed in the casing. In the preferred embodiment, the casing has a configuration generally in the form of a segment of a cylinder, and the adapter has a segment configuration so that the casing and adapter present a generally cylindrical profile when joined. This arrangement permits using the same basic meter movement and casing to produce meters of different operating characteristics. The meter either with or without the adapter can be inserted through the usual circular opening of a mounting panel. The casing has toothed sides to retain a quick connect panel nut used to secure the meter to the panel.

Abstract: A power supply for realistically controlling a model railroad engine. For engine acceleration, the power supply provides an output signal having a linear ramp with pulses superimposed thereon. For constant speed operation, the supply produces a constant output voltage. For deceleration, the power supply produces a decreasing linear ramp signal with pulses superimposed thereon. Adjustment circuitry is provided for modifying the output waveshape so that realistic control can be achieved for different model engines having different operating characteristics.

Abstract: A video system having a transmitter in which a composite signal is formed by combining digital information with scanlines of an analog video signal generated by a line scanning device, and a receiver in which the digital information is recovered. The digital information is combined with the analog video signal at predetermined locations along scanlines of the video signal, and these predetermined locations are varied in order to prevent visible deterioration of the video image. In the video receiver, the digital information is recovered by examining the composite signal at the predetermined locations to extract the digital information. Each bit of digital information to be conveyed is represented by a first pseudo-random digital pulse sequence (or its complement, depending on whether the data bit is 1 or 0) which is superimposed on a selected scanline of the analog video signal to form the composite signal.

Abstract: An electric meter particularly characterized by a small number of moving parts and simplified assembly. A coil assembly initially including integral support elements which permit connection of pivot bearings or taut bands is adapted to be accurately positioned for rotation on the supporting base by inserting the assembly into the base. Cooperating locating surfaces on the base and coil assembly provide for accurate positioning of the support elements so the axis of rotation of the coil is in a predetermined position relative to a magnetic circuit of the meter. After insertion of the coil assembly, the bridging elements are severed. A coil support form of unique construction includes motion limiting elements which cooperate with surfaces of the magnetic circuit to limit the permissible extent of movement of the coil, in the event of shock or impact, to positions well within the elastic limit of the supports which mount the coil for rotation.

Abstract: In a multi-device data transmission system with source and acceptor devices linked by a data highway and handshake lines, provision is made for automatically adjusting the delay of the handshake cycle to suit the highway length and other determinative factors. This is achieved in that the acceptors do not accept data until told so to do via one handshake line, whereas the source is only allowed to issue this command when it has been told via another handshake line that all acceptors have seen the data. The system determines its own delay in this way and automatically adapts the delay to whatever length of highway is employed, whether a fraction of a meter in a circuit board or several tens of meters in inter-rack wiring.

Abstract: In a DVOM of the dual slope type, an unknown resistance or conductance to be measured is connected to a reference signal source to generate a voltage or current which is measured by the DVOM. However, if the input impedance of the DVOM is not extremely high, it loads the unknown resistance or conductance, and renders the relationship between the value of the unknown resistance or conductance and the actual voltage or current measured by the DVOM non-linear. In order to correct for this, a proportion of this actual voltage or current is algebraically summed with the reference signal used in the DVOM for generating the second slope of its dual slope operation, the proportion being selected in dependence on the input impedance of the DVOM (which can thus now take any convenient value) to linearize the relationship between the value of the unknown resistance or conductance and the output signal of the DVOM.

Abstract: A bipolar reference voltage source comprises first and second ratio-matched transistors having respective collector load resistors and arranged to pass slightly different currents. The emitter of the first transistor is connected to two emitter resistors in series, while the emitter of the second is connected to the junction between the emitter resistors. The bases of the transistors are commoned, while their collectors are respectively connected to the two inputs of a differential amplifier. A switching arrangement has a first state in which the output of the differential amplifier is connected to the bases of the transistors, and the end of the two emitter resistors remote from the transistors is grounded, thereby producing a first reference voltage of one polarity at the output of the differential amplifier.