Abstract: An electromagnetic relay has a tongue armature disposed inside a hollow coil body and having a free end movable between two cooperating pole plates, and a fixed end having an additional spring section disposed at an angle with respect to the movable portion of the armature, the spring section being secured to one of the coil flanges, thereby extending the effective free spring length of the armature so as to improve the sensitivity of the relay. The position of the armature with respect to the pole plates is adjustable after encapsulation of the relay by irradiating the spring section of the armature with thermal pulses, such as laser pulses at specified locations.

Abstract: The rotating armature relay exhibits one or two ferromagnetic bars which are provided with an insulating covering in their central area. Contact springs are secured in the insulation covering, the contacting, free ends of said contact springs respectively interacting with cooperating contact elements anchored in a base body. As a result, a slide-free and, thus, low-friction actuation derives as, however, does relatively high friction at the contact locations, whereby contact impacts are suppressed and foreign layers are abraded from the contact surfaces.

Abstract: There is provided an add-on terminal connector assembly for electric control devices used in motor control centers that eliminates the conductor bends necessary to route incoming conductors to the terminals of a control device which is mounted in the control center.

Abstract: A proportional solenoid consisting of a stationary pole piece of ferromagnetic material which has a radially externally facing frusto-conical section surrounding a cylindrical recess in the stationary pole piece. Both the stationary pole piece and armature are fitted into the bore of a guide tube. Thus, the bore of the guide tube provides the required concentricity between the movable armature and the stationary pole piece. The movable armature is provided with an integral reduced diameter cylindrical nose that is complimentary to the cylindrical recess of the stationary pole piece.

Abstract: An electromagnetic relay comprising a bobbin on which a winding is wound, a base block on which an armature and contact elements are mounted, an approximately U-shaped magnetic pole piece, and an approximately U-shaped magnetic yoke piece. The long tongues of the magnetic pole piece and the magnetic yoke piece are inserted into the bobbin, while the short tongues of the magnetic pole piece and the magnetic yoke piece are inserted with a gap into the base block.

Abstract: A detent mechanism for a manually activated transducer is disclosed in which the transducer element is movable along a predetermined path by means of a handle and includes a sensor for scanning markings on the transducer element and includes first and second components that determine the magnetic field in an air gap. These magnetic components have spaced, adjacent grooves directed in the direction of movement of the rotating transducer element. The magnetic forces created between these first and second components serve to hold the transducer element in one of a plurality of definite positions.

Abstract: In a thermal switch for temperature control of electrical heating apparatus, a contact reed is integral with a terminal and is rigid except for a relatively short longitudinal area so that, when the contact reed is acted upon by a bimetallic disk spring, a hinge type movement of the contact reed will result.The integral rigid design of this component designed as terminal and contact reed makes keeping the geometric conditions within the thermal switch, especially the space between the contact reed and the bimetallic disk spring, at closer tolerances, much easier than with prior leaf springs used as a contact reed. Accomplished thereby is a more dependable switching performance and thus a quality improvement in large-scale manufacture and a reduction in manufacturing costs.

Abstract: A sliding rheostat includes two slider supports mounted to a support member between a pair of resistance base plates and in the direction that the slider supports move. Screws are mounted between the corresponding sliders and the support member to adjust the positions of the sliders relative to the support member, thus permitting the points at which the sliders are in contact with their respective resistance base plates to be placed in a line.

Abstract: A circuit for sampling the conditions of a liquid level sensor for a short period of time after the circuit is turned on and energizing a warning indicator for an initial check-out period that is followed by continuous energization in the event the sensor indicates a low liquid level condition during the sampling period.

Abstract: A vehicle alarm system sensing unauthorized use of the vehicle and providing a warning signal for a predetermined warning time interval which may be extended as desired. A latching circuit includes a bistable flip-flop with a capacitor discharging through a voltage divider circuit to define an extended warning time interval. Logic gates are switched to change the voltage divider circuit voltage reference levels to charge the capacitor during a predetermined exit time interval to inhibit warning signal actuation when exiting the vehicle. A re-entry timer is included to inhibit warning signal actuation when re-entering the vehicle.

Abstract: A method and apparatus for very rapidly determining a minimum or maximum data word from a list of such words in which the expected time for completing the determination of the minimum or maximum value decreases as the number of words in the list is increased. Each data word is stored in a dedicated processing element. Each processing element first outputs onto an open-collector bus a "0" in a position corresponding to the highest order "1" bit in the stored data word. The data signal thus assembled on the bus thus has a "0" at positions corresponding to the highest order "1" bit of each of the processing elements. In response to this data signal, a single controller transmits back to the processing elements a control signal having a "0" in and only in the lowest order "0" bit of the data signal received on the bus.

Abstract: The ladder network of a recirculation of remainder analog to digital converter has pairs of controlled switches connected alternately to a voltage source and a ground, to establish unidirectional current flow through the switches. Unidirectional current flow eliminates ladder error caused by current flow direction resistances inherent in the switches.

Abstract: A differential voltage amplifier comprises a first and second capacitive coupling type amplifiers in each of which an autozeroed mode period for setting an operating point and a signal amplifying mode period for amplifying an input voltage are alternately set up, and the autozeroed mode periods in said first and second amplifier are shifted from each other, first and second mode selector for alternately setting up the autozeroed mode and the signal amplifying mode in the first and second capacitive coupling type amplifiers, first and second signal selectors provided corresponding to the first and second capacitive coupling type amplifiers, the first and second signal selectors alternately selecting a reference voltage and an input signal voltage to apply the selected signal to the first and second capacitive coupling type amplifiers, the first and second signal selectors further selecting the reference voltage corresponding to the autozeroed mode periods of the first and second capacitive coupling type amplif

Abstract: A digital-to-analog signal converter (1000) provides an analog output signal by subtracting bit currents reflecting a digital input signal from a constant current source (1004, 1018-1022) at a current summer (1003), with the difference current being applied to a constant load. The subtracting of the current, rather than switching the current, avoids the modulation of an associated power source since the total current demand remains the same. In that low power operation is possible, the converter is particularly suited for use in an arrangement where only a low level of operating current is available from a power source.

Abstract: A digital-to-analog converter of the current-adding kind includes n input buffer circuits to which the bits of the digital signal are applied in parallel, a first ladder resistor network having n resistors connected in series to which complementary outputs of the input buffer circuit are connected, a second ladder resistor network for dividing output terminal voltages from the first ladder resistor network into 2(2.sup.n -1) voltages, (2.sup.n -1) switching circuits having inputs connected to voltage dividing points of the second resistor network, and a common summing resistor connected to the outputs of the switching circuits to add currents supplied thereto, thereby providing an analog voltage having a level corresponding to the numerical value of the digital input signal.

Abstract: An integrated array of pressure transducers capable of producing an analog output voltage representative of the applied pressure is proposed. The individual transducing elements (16) are defined by a three-layer structure including a thin layer of piezoelectric material (10) disposed between a reference potential plate (12) and a plurality of electrodes (15) contained in a silicon substrate (14). A force applied to a localized portion of the reference plate will cause a deflection of the piezoelectric material towards the electrodes on the substrate, inducing a capacitive charge on the electrode in the localized area. This capacitance is stores at a node A associated with the transducing element, and may be interrogated by a sensing circuit (18) located in the silicon substrate. Since the induced charge is directly proportional to the applied force, a measurement of the output voltage from node A will yield a direct indication of the localized force applied to the sensor.

Abstract: An anti-security control for unlocking the normally locked door which separates the corridor side and the stairwell side of buildings, such as hotels. The anti-security control is preferably adapted for use with and draws power from any conventional-type of smoke and fire detection and alarm system. When the detection and alarm system senses the existence of a dangerous level of smoke or fire, current is shunted to a solenoid which operates to unbolt the normally locked separation door. A depressible button may be operatively affixed on the corridor side of the door to provide access from corridor to the stairwell regardless of whether a smoke or fire condition is sensed by the detection system.

Abstract: A battery-powered photoelectric smoke detector periodically samples the air in a smoke chamber. A manually-operated test button is provided for simulating smoke to test the device. The sampling frequency is determined by a first resistance. A frequency changing circuit includes a test switch, the movable contact of which is coupled to the test button and is responsive to operation thereof for connecting it parallel with the first resistance the series combination of a diode and a second resistance for increasing the sampling frequency. Means are provided for back-biasing the diode to disable the frequency changing circuit when the detector detects smoke.

Abstract: A combined communication, security and alarm radio system for supervising equipment in a plant or installation, in which a base transmitter/receiver (4) is in two way communication with a remote control unit (2). A plurality of portable transmitter/receiver units (12) enables direct communication between operators through the base transmitter/receiver unit (4). An alarm message unit (8) connected to both the control unit (2) and a telephone exchange landline enables pre-recorded messages to be transmitted in sequence to a plurality of subscribers. Each portable transmitter/receiver unit (12) has a push button (27) to activate the alarm message unit (8) through the base transmitter (4) each being recognizable by its own tone. The system also includes a paging transmitter (6) and up to as many paging receivers (14) as there are portable units (12).

Abstract: The present invention provides an antitheft system comprising a pair of spaced coils which are excited to produce an alternating magnetic field within a surveillance zone between the coils. Thus, a magnetic marker having a permeability of less than 150,000 and a coercive force of substantially 2.5 MA/CM which is carried through the surveillance zone cuts or links lines of magnetic flux within the zone regardless of the orientation of the marker. Electronic circuitry detects the electromagnetic field within the zone at harmonic frequencies greater than the frequency of the oscillating magnetic field and, through coherent correlation, determines the presence of the marker within the surveillance zone as well as distinguishing and differentiating the marker from other ferromagnetic materials.

Abstract: A portable device for detecting when undergarments are wet with urine comprises electronic disposable sensor means in contact with said undergarment, an electronic detector means activated by said sensor means, and an alarm means activated by the detector means, all chosen and constructed such that there is no energization of any part of the system until a wet condition is detected and such that there is no possibility of more than 9 volts of electric potential in contact with the human body, with the current generated by said potential not to exceed 10 microamperes.

Abstract: The disclosure relates to bed departure detection devices employing tape switch detectors in fixed positions in the seat and thigh sections of the mattress supporting structure of an articulated hospital bed. Bedside circuitry, connected to existing nurse call and two-way communication links, provides signals to a central nurse call station as an indication of unauthorized bed departure.

Abstract: The surface of a material is inspected for defects by visual examination of a television picture of the surface produced by at least one camera focused on the material and transmitting an image to a screen in the form of a video signal. The connection between screen and camera is made only when a defect is detected on the surface of the material. The video signal is delimited by an upper and a lower signal level which, if exceeded, results in a trigger signal being activated. In addition a trigger mechanism and an image storage facility are provided between the screen and the camera. Appearing on the screen are only pictures of surface areas showing defects; areas without defects are not displayed on the screen.

Abstract: Current provided to a generally constant impedance load is monitored to detect a predetermined load current decrease not resulting from normal load voltage fluctuations, such decrease indicating an abnormal increase in load impedance. A latching alarm is actuated when the predetermined load current decrease is detected. The degree of load current decrease tolerable without activating the alarm is determined by a user-adjustable percentage-of-change sensitivity control. A logic gate blocks alarm functions when the load current decreases to an abnormally low level. The disclosed device can be used to monitor the status of a line voltage energized heat trace cable constituted by a plurality of parallel-connected resistance wire heating elements. Multiple monitoring devices can be used in conjunction with a master alarm which can be reset without resetting the particular monitoring device alarm that triggered the master alarm.

Abstract: A line drawing method for display apparatus having memory means for storing line information including the start point and end point of any line which has been displayed on the display screen, comprising the steps of entering start point data and a line drawing instruction for a line to be displayed on the display screen, determining the end point of the line to be displayed in accordance with the entered information and stored line information, generating line information based on said determination, storing the generated information in the memory means, and displaying the generated information on the display screen.

Abstract: An all electronic interconnect system having high flexibility, low cost, and higher reliability. A central matrix is formed from a multiplicity of solid state analog switches in which each switch is controlled by a digital address. Each switch can connect a common switch point to one of a multiplicity of outputs. For use with digital devices such as computers and peripherals, a multiplicity of rows of the matrix may be connected to accept an N-bit parallel byte and to output such an input selectively to one of several channels. The channel to which the input is connected is selected by a digital address to each of the analog switches in the row. By using a multiplicity of rows, the matrix is built up to interconnect a number of input digital devices to a number of output devices through control of the electronic addresses. Control circuits are provided which permit rapid interconnection of any input device to any output device.

Abstract: An FM/CW radar linearization network provides target identification data discriminating a target from background reflections and/or false targets by compensating for random variations in the linearity of the frequency sweep of the radar transmitter in the processing of the radar receiver signal, the latter being characteristic of the range and physical size of the target. Linearization is achieved by sampling the transmitter signal, generating an error signal proportional to and indicative of any deviations in the frequency sweep of the transmitter from that for linear operation, and applying that error signal to correct the target data signal, thereby frequency normalizing the same for processing and utilization.

Abstract: An auto notch system which automatically "notch" filters up to four interference signals (interferers) in the band from 50 KHz to 150 KHz comprises a signal detector, an adjustable notch filter, a bandpass receiver and a digital controller, plus the software that runs in the digital controller. The signal detector circuit has an antenna, a preamplifier and a group of "fixed" filters. The adjustable notch filters are four circuits, each includes an active notch type filter stage with a DAC (digital to analog converter) in series with the input resistor to allow gain control and another DAC that controls the current through a diode that is optically coupled to a light dependent resistor pair. The light resistor pair is in the filter loop and as the resistance varies the frequency response of the filter changes. Thus the frequency response is controlled by varying the diode current.

Abstract: An improved microwave field monitor device is disclosed characterized by use of a microstrip antenna and control electronics adapted to provide a field alarm, field monitor, accumulated dose alarm, and integrated dose indication of RF radiation exposure to an individual. The monitor is packaged in a small configuration similar to an identification badge adapted to be easily affixed to the clothing of a user. The monitor additionally is capable of measuring the RF radiation exposure at particular part or whole body resonance frequency bands or standing wave hot spots known to be hazardous to individuals.

Abstract: Ink jet apparatus for utilizing hot melt ink is provided, comprising a printing head and a reservoir for holding a supply of hot melt ink, the reservoir having a normally open port or fill tube with an end face residing within the volume of the reservoir, the end face being located at about the volumetric center of the reservoir. The reservoir is maintained with an ink volume of no more than about half of the reservoir volume, so that ink can not spill through the normally open port when the apparatus is tilted.

Abstract: An ink jet recording apparatus has an improved head plate having a plurality of recording heads, a plurality of openings corresponding to the outlet port of each recording head, and a guide groove to lead ink liquid from the openings to a discharge port, the guide groove being gradually tapered downwardly to the discharge port.

Abstract: A stackable fluid dispensing apparatus has a case and a fluid manifold located within the case which is adapted to be connected to a source of pressurized fluid. A plurality of valves located within the case are connected to the fluid manifold by a plurality of fluid lines. A nozzle block on the case has a plurality of fluid dispensing openings positioned within an exterior face of the nozzle block in at least one line. Fluid tubes communicate each of the valves with a selected one of the nozzle block openings whereby actuation of the valves controls the flow of the fluid through the nozzle block openings. The dispensing openings at the outermost extents of the line in the nozzle block are located adjacent opposite edges of the exterior face. The distance from the center of each of the opposite outermost dispensing openings to the respective adjacent edge of the exterior face is one half the center to center distance of any two remaining dispensing openings in the line.

Abstract: Disclosed is a thermal printing system in which, an auxiliary heating means is driven to heat a main heating means for dot printing to a print feasible temperature, and at the time of dot printing, the main heating means is heated to the said print feasible temperature. The main heating means and the auxiliary heating means are both disposed on the surface of a radiating substrate. The thermal head apparatus is thus simple in construction and capable of improving printing speed.

Abstract: An optical recording medium containing a light-absorbing film of refractory material less than 60 nm thick and selected from carbides of Al, Hf, Nb, Ta, Ti, V, W, and Zr and alloys herebetween, whereupon localized heating of the light-absorbing film enables information storage in the form of localized features in the heated areas which can subsequently be optically detected and can be used as a master information record for replication purposes.

Abstract: An optical disk unit, of the kind having a record element and a flexible cover sheet that are attached around an outer periphery in a manner providing an outer spacing and a generally enclosed inter-space therebetween, has an improved construction which significantly reduces the likelihood of contact between the record element and cover sheet. Central spacing means provide a central sheet-to-element spacing that is significantly larger than said outer spacing and vent means, into and out of the inter-space cause a reduction in the spacing between the record portion of the element and the cover sheet during write/read operation. The air flow through the vent means also reduces the formation of visible debris in the enclosed record element/cover sheet inter-space.

Abstract: A pen capping mechanism for use in an X, Y graphics plotter, or the like, having a plurality of pens with writing tips requiring sealing between periods of use. A flat bar of plastic is provided as a slider member with an upper surface adapted to sealably mate with the tips of the pens. The slider member is supported for longitudinal movement on a support track and is moved between positions by an operator connected thereto. The member has a plurality of bores therethrough through which respective ones of the pen tips can pass in order to write. The bores are positioned such that as the member is moved through the various operative positions, respective ones of the bores come into alignment with a pen tip such that only one pen tip at a time is in alignment with one of the bores.

Abstract: In an illustrated transducer construction, electric potential changes applied to the transducer effect piezoelectric movement for causing recording fluid to be ejected through a jet orifice and applied on a recording carrier. In order to increase the maximum drop frequency and in order to improve the drop formation and drop speed, in accordance with the disclosure the linear distance of the connection points of the two ends of each transducer with the orifice plate is smaller than the length between the connection points as measured along the transducer. The transducers are thus mechanically prestressed to assume an arcuate configuration so that, in the rest state, recording fluid is disposed between the transducer and the plate. Given an electric driving pulse the transducers are shortened and conform with the plate in a planar fashion. Immediately after the excitation, each transducer returns to its arcuate initial configuration.

Abstract: An electrolytic print head comprises a plurality of styli (16, 18) between electrically insulative laminae (38, 42, 48, 38', 42', 48') which space the styli from planar reference electrodes (20, 22, 24). The styli and reference electrodes are fabricated of a mixture of ruthenium dioxide and corrosion resistant glass, and the insulative laminae are fabricated of corrosion resistant glass. The method of manufacture of the print head facilitates use of styli and reference electrodes requiring high temperature processing prior to deposition of metal conductor tracks for the styli and reference electrodes.

Abstract: A heat sensitive record material comprising a support sheet and a heat sensitive record layer formed on the support sheet, the heat sensitive record layer being composed essentially of a colorless or light-colored electron-donating colorless dye, an acidic substance which is thermally reactive with the electron-donating colorless dye to develop a color and a binder, characterized in that said heat sensitive record layer contains an effective amount of at least one anilide compound represented by the general formula: ##STR1## where R.sub.1 is an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group; R.sub.2 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a sulfamoyl group or a halogen atom; R.sub.3 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or a halogen atom; and n is an integer of 0 to 5.

Abstract: A heat sensitive recording material is described, which has on a support a heat sensitive coloring layer containing (a) an electron-donating colorless dye, (b) an electron-accepting compound, and (c) at least one ether compound represented by formula (I) or (II) ##STR1## wherein X represents a hydrogen atom, a halogen atom, an alkyl group containing not more than 6 carbon atoms, or an alkoxy group containing not more than 6 carbon atoms; Y represents a hydrogen atom, a halogen atom, an alkyl group containing not more than 6 carbon atoms, or an alkoxy group containing not more than 6 carbon atoms; and R represents a hydrogen atom or an alkyl group containing not more than 18 carbon atoms.

Abstract: This invention relates to mono- and bis(aryl- and/or heteroaryl)-substituted-phthalazinones, phthalimidines, pyridopyridazinones and pyrrolopyridinones useful as color-forming substances, particularly in electrochromic recording systems, which are prepared by the interaction of a mono- or bis-substituted-phthalide or furopyridinone with a substituted or unsubstituted hydrazine.

Abstract: A semiconductor device includes a dynamic memory area formed in a semiconductor substrate and set in an inequilibrium potential state, and a plurality of MOS transistors which emit minority carriers or more than a predetermined number into said semiconductor substrate during operation in a saturation region. Each of the MOS transistors is so arranged that a prolonged line extending in a direction from the source region to the drain region may cross the dynamic memory area.

Abstract: A transferred electron semiconductor device in the form of an oscillator, for example, is fabricated by a molecular beam epitaxy growth process wherein a plurality of semiconductor layers are sequentially grown on a planar substrate. A pair of ohmic contacts are formed on the outer surface of the substrate and the uppermost layer with the resulting structure including two distinct intermediate semiconductor regions, the first being a drift region adapted to exhibit a differential negative resistance due to the transferred electron effect, and the second being a planar doped barrier region for accelerating electrons into the upper valley and injecting them into the drift region. By the use of a planar doped barrier a more uniform electric field is obtained along with a controlled lower barrier height whereby the transfer of electrons to the upper conduction band satellite valley can be made to occur over much shorter times and distances thus extending the upper frequency range of operation.

Abstract: A semiconductor device comprising a semiconductor substrate, a first insulating layer formed on the semiconductor substrate, a bonding pad formed on the first insulating layer, a conductive layer formed on the first insulating layer and adjacent to the bonding pad, and a second insulating layer formed to cover the conductive layer characterized in that the surface of the second insulating layer formed on and near the conductive layer is made at the same level as or lower than the surface of the bonding pad.

Abstract: An improved digital integrated chrominance-channel circuit having gain control for color-television receivers includes at least one integrated circuit for digitally processing the composite color signal. The circuit includes a first limiter inserted between a parallel multiplier and a burst-amplitude-measuring stage, and a control stage including a parallel subtracter whose minuend input is fed with a reference signal, and whose subtrahend input is connected to the output of the burst-amplitude-measuring stage. A digital accumulator whose enable input is presented with a signal derived from the trailing edge of a burst gating signal is used as an integrator.

Abstract: A television camera which carries out color separation by use of vertical correlation in a picture, comprises a pickup element for scanning a target, a color separating stripe filter, and an optical filter for separating a single incident light beam in a direction which is the same as the scanning direction of the pickup element and a direction perpendicular to the scanning direction, by acting on the single incident light beam in two dimensions. The optical filter comprises a first double refraction transparent plate for separating a light beam in a direction which coincides with the scanning direction of the pickup element, a second double refraction transparent plate for separating a light beam in a direction which is rotated by 45.degree. with respect to the scanning direction, and a third double refraction transparent plate for separating a light beam in a direction perpendicular to the scanning direction. The first, second, and third double refraction transparent plates are stacked.

Abstract: A previewer provides for the dynamic viewing of an article desired to be worn by the user in a complete series of poses without actually trying on the article. The image of the article is computer generated, and a large plurality of articles are available for previewing. The user pre-records, or creates in realtime, a series of poses which are time-framed and position orientation coded, which coded information is read by the computer and the computer generated article image is then re-imaged in accordance with the accessed coded information, and the re-imaged article image and the user video image are then video mixed, optically mixed, or superimposed in digital image storage memory, so that a user plus article composite image may be viewed by the user. The previewer is useful for previewing various articles or accessories, or combinations thereof, such as eyeglasses, hats, hairstyles, wigs, make-up, cosmetic surgical changes, clothing, furnishings, and automobile accessories.

Abstract: An interface module for a video endoscopic system that permits the insertion tube to be connected to and disconnected from a video processor quickly and easily whereby sterilizing the tube is simplified and the substitution of one tube for another is greatly facilitated. The connector module interfaces the various video and other electric connections and also interfaces a fiber optic bundle connection and a fluid supply connection between the processor and insertion tube. A solid state imaging device is located at the distal end of the insertion tube, and this device is driven by signals received from the processor and transmits video signals back to the processor. The interface module contains circuitry that accepts standard input signals from the processor for driving the imaging device, and this circuitry includes means for adjusting the input signals so that they are compatible with the particular imaging device in the tube.

Abstract: A video processing system especially for use with microprocessors or microcomputers characterized by limited memory storage capacity and processing capability. The video processing system includes a TRANSITION DETECTOR for detecting BLACK-TO-WHITE and WHITE-TO-BLACK transitions in a video signal, from whatever source. The output of the TRANSITION DETECTOR may be coupled to a FEATURE COUNTER so that the FEATURE COUNTER provides at a computer buss an output indicative of the number of such transitions occurring during a particular horizontal scanning period. The output of the TRANSITION DETECTOR also drives a SHIFT REGISTER that selectively disables a plurality of FEATURE TIMERS, each of which has an input coupled to a CLOCK so that the FEATURE TIMERS provide an output indicative of the time duration between the beginning of a horizontal line and successive transitions in the video signal.

Abstract: An apparatus is described which is capable of producing an image of a smelt bed of inorganic chemicals collected at the bottom of a kraft pulp recovery boiler. The image produced is free of interferences of fume particles and gaseous radiation which have obscured prior attempts to view hot surfaces under such environmental conditions. The apparatus includes an industrial closed circuit video camera fitted with an infrared imaging detector or vidicon tube. An objective lens obtains the image. An optical filter interposed between the lens and the vidicon is a key element of the invention and is selected to reject radiation less than about a micrometer to avoid fume interference. The filter is further selected to reject all but limited ranges of radiation to avoid gaseous species overlying the smelt bed which are strongly emitting and absorbing. As an example, a spectral filter centered at 1.68 micrometers with a band width of 0.07 micrometer is suitable for imaging a kraft recovery smelt bed.