Abstract: A closed-loop hydrostatic drive unit having a variable displacement fluid pump driven by an electric motor for generating high-pressure fluid adapted to be communicated to a fluid motor and returned to the fluid pump via a high-pressure filter. The closed-loop hydrostatic drive unit is mounted to a rectangularly-shaped reservoir housing having upper and bottom surfaces connected by side walls and end walls to define therein a chamber for the storage of fluid at a low pressure which is communicated to the fluid pump via a charge pump and suitable conduits and check valves. In a first embodiment of the invention the interior of the reservoir housing is divided by means of a partition to define the fluid-holding chamber, while the remaining portion of the reservoir housing defines a separate chamber for the mounting and storage of the high-pressure filter and/or other selected fluid power components.

Abstract: Apparatus for fire protection purposes including a compressed-gas cartridge device with at least a thermally responsive triggering mechanism. The triggering mechanism includes a striker for forcibly being driven toward the compressed-gas cartridge device and a locking device for maintaining the striker at a spacing from said compressed-gas cartridge device by engaging a portion of said striker pin with one end portion thereof. Another end portion of the locking device is biased against a blocking device with the blocking device being disposed between the another end portion of the locking device and an abutment member. The blocking device is responsive to the exceeding of a predetermined temperature for enabling displacement of the locking device out of engagement with the striker thereby permitting movement of the striker toward the compressed-gas cartridge device.

Abstract: Method and apparatus for controlling a well providing access to an underground source of high temperature geothermal brine against flashing as the hot brine is delivered upwardly through the well to surface power apparatus for use of heat from the brine in the generation of electrical power, thereby eliminating plugging of the well by precipitated mineral deposits as well as other problems which have heretofore caused most geothermal resources of this character to be beset with operational problems. A pump down in the well pressurizes the hot output liquid that is delivered to the surface generating equipment against flashing, the pump having a novel long tailpipe suspended therefrom which extends deep into the well.

Abstract: A steam turbine power plant having associated therewith a closed loop flow arrangement for extracting heat from the power plant and supplying the extracted heat to an external heat load. Included within the flow arrangement is a predetermined number of heater elements, each of which extracts steam having a predetermined heating capacity associated therewith from a predetermined number of separate locations within the power plant. The heat so extracted is transferred to a heat transfer medium flowing at a predetermined flow rate within the closed loop arrangement. The extracted heat is exchanged to the heat load within a heat exchanger element connected within the flow arrangement. The amount of heat extracted from the power plant is functionally related to, and automatically limited by, the flow rate of the heat transfer medium within the closed loop arrangement. The flow rate of the heat transfer medium is itself functionally related to the flow rate of the motive fluid for the power plant.

Abstract: An oil-retaining boom structure for disposition upon a body of water, preferably surrounding an off-shore oil well has a plurality of bouyant float members movably connected together by a connecting cable which extends through the body structure of each float member. Each float member comprises an elongate housing having weights disposed in one end thereof adapted to retain that housing end downward in the water. The floats are interconnected with each other through the connecting cable with washer means surrounding the cable between the adjacent floats. The washer means preferably have grooved means surrounding the circumference of the washer to accommodate elongate rods which can be used to retain portions of the boom in parallel relationship if desired to form a channel for the oil within the boom. The floats have sheet means attached to at least one side thereof extending along the boom to retain the oil on one side of the sheet means as the boom rides at or near the surface of the water.

Abstract: A method of and apparatus for the installation and retrieval of instrumentation hardware supported through a hole in a section of ice is provided wherein an expansion member such as an inflatable bladder is utilized for displacing water normally subject to freezing within the hole. The inflatable bladder comprises an elongated expandable sleeve of sufficient length to substantially extend the ultimate depth of the hole in the ice for engaging and bearing against the sidewalls thereof. A portion of the hardware adapted for the surface support thereof may be disposed within the bladder as well as therebeneath and may be retrieved at a date subsequent to installation by deflating the bladder without the problem of said hardware being frozen in or beneath the ice.

Abstract: A method of constructing pre-tested concrete pilings and pile caps particularly for use in supporting structures, such as transmission line towers that are subjected to large overturning moments. One or more pile holes are bored, a small diameter sheathing containing one or more steel tendons is inserted and a concrete mixture is poured in the pile hole exterior of the tendon sheathing with the tendons anchored in the bottom of the pile. When the concrete has obtained sufficient strength, the tendon is stressed, thereby testing the tension-carrying capacity of the pile and its surrounding foundation soil. A concrete pile cap is thereafter joined to the pile, the tendons are again stressed and anchored to the pile cap and the tendon sheathing is filled with concrete grout to form a solid post-tensioned foundation that has been pre-tested at a force in excess of its design load.

Abstract: A submergible chamber is provided with flanges at the outward ends of chamber guide arms, wherein each flange engages a stanchion. In one embodiment the flanges are selectively electromagnetic with the stanchions, and with sufficient force, the flanges are held to the stanchions thereby positioning the chamber at a specific depth. In another embodiment, the flange is adapted to pivotally grip the stanchion, and further each stanchion is provided with a vertical gear rack engaging the driven gear of each respective work arm so as to accurately position the chamber at a specific depth whereat the clamp holds the chamber at that depth.

Abstract: A trench cutter for excavating trenches and for laying water pipes and drainage pipes into trenches consisting of a travelling cutter chain with a jib supporting the cutter chain, the jib being pivotable in a vertical plane. A pipe laying duct is included for entering the excavation and sliding on the bottom of the excavation trench, the laying duct being pivotably connected to the jib. A duct guide arm extends parallel to the back surface of the pipe laying duct for supporting the duct vertically so that it faces the cutter chain. A plurality of parallel guide rollers have one end pivotably connected to the duct guide arm and their opposite end connected to the outward drive shaft of the trench cutter. The drive shaft of the trench cutter is pivotably connected to the free end of the jib.

Abstract: A system and method for emplacing a relatively large casing under and spanning an obstacle such as a river is disclosed. The casing is emplaced along the path of a previously bored and placed existing pilot string running beneath the obstacle. The pilot string extends typically in an inverted arcuate contour from a first position at or near ground level on one side of the obstacle to a second position at or near ground level on the other side of the obstacle. The system includes apparatus for concentrically reaming the pilot hole to an enlarged diameter and entraining the cuttings from the excavated annulus of the reaming operation in drilling mud. The casing is advanced along the reamed pilot hole in following relationship to the reaming apparatus. A seal is provided between the outer surface of the leading portion of the casing and the reamed pilot hole so that the drilling mud containing the entrained cuttings flows into the leading end of the advancing casing.

Abstract: Apparatus for constructing an underground tunnel employs a drive shield composed of elongate drifting cutters disposed side-by-side in a circular configuration around a support frame. Hydraulic rams serve to advance the cutters and to shift up the frame when all the cutters have been advanced. The cutters have rear end portions which engage on a follow-up ring behind the drive shield.A platform is supported by the frame within the shield and carries some form of working appliance for detaching and removing the debris material. The platform also carries a rotatable concrete spraying device which serves to seal and secure the tunnel wall exposed when the follow-up ring is shifted up to the shield.

Abstract: The invention relates to an open frame offshore foundation structure of concrete to be firmly but removably located on the sea floor. The structure comprises a lower set of hollow columns inclined towards each other in direction upwards, a ballastable intertie box structure rigidly receiving the tops of said inclined columns and an upper vertical column unit, the lower ends of which are rigidly connected to the intertie box structure and the upper end of which shall support a working platform in position above sea level.

Abstract: A tool for positioning and holding pipe to be laid in a ditch at a desired level while the ditch is filled partially with rock, gravel, etc. The tool comprises a rod located in a tubular member and having a pointed end extending out of the tubular member. The tubular member and rod are movable axially relative to each other. A locking member is provided for securing the rod and the tubular member at a desired position relative to each other. A pipe supporting means is carried by the tool and is fixed in place relative to the tubular member. In addition, a pipe locking means is supported for movement between a closed position and an open position. In the closed position, the pipe locking means forms an enclosed or partially enclosed configuration with the pipe supporting means for holding the pipe in a position such that its axis is generally transverse with the axis of the tubular member or that of the rod.

Abstract: A method and machine are disclosed herein for cleaning and restoring sand beaches which have become contaminated by oil spills. The machine travels on the beach and sprays liquid nitrogen onto the contaminated area, thereby solidifying the oil and sand mixture so that the mixture can be separated from the underlying uncontaminated sand and be efficiently removed from the beach and transported to a remote site for disposal or further treatment.

Abstract: The combination with an air conditioning system including compressor, condenser and evaporator, with a humidifier for humidifying conditioned air and a heat exchanger for transferring heat between hot refrigerant of the air conditioning system and water supplied to the humidifier.

Abstract: An elastic dampening roll cover knitted in the form of a tubular sleeve comprising knitted courses and wales of inelastic absorbent yarn, with an elastic yarn interlaced with the courses and wales around the circumference of the tubular sleeve, said inelastic absorbent yarn comprising a substantially inelastic air-bulked yarn having a plurality of substantially continuous filaments which are individually convoluted into coils, crunodal loops and whorls at random intervals along their length and the surface of said yarn having a plurality of crunodal loops irregularly spaced therealong, said elastic yarn comprising an elastic core strand and a wrapping strand associated with the elastic core strand in the form of doubled-back loops wound with false twist for a multiplicity of turns around the circumference of the elastic core strand.

Abstract: Locomotive environmental system to be mounted in the roof of a cab for controlling the environment within the cab which includes a housing having an upper chamber arranged above the roof line of the cab and having one compartment for a condenser unit and another compartment for a compressor unit, a blower in the compartment housing the condenser unit for circulatng air through the condenser compartment and also through the compartment housing the compresser unit, a lower chamber arranged below the roof line of the cab and housing an evaporator unit for the system together with blower means for circulating air through the lower chamber and the cab, wherein the motors for the compressor unit and the blower associated with the condenser unit are driven by the same source of variable power.

Abstract: A vehicle eutectic plate refrigeration system provides simultaneous defrosting of part of the plate exterior surface, all of the secondary heat transfer surface and freezing of the eutectic solution within the plate. This system thus preserves sufficient space for air passage, which otherwise would be blocked by frost and ice. The system utilizes the normally rejected heat to perform a defrosting function and utilizes the ice and frost to perform the refrigerant condensing function. Hot gas from the compressor is diverted through the defrost coil where the refrigerant is for the most part condensed before it is passed through the condenser. The liquid refrigerant from the condenser is then used to freeze the eutectic solution within the plate.

Abstract: A contoured finger ring has a finger receiving aperture with five approximately equal sides and which is configured to pass the knuckle therethrough while the ring is at a ninety degree angle to its proper position thereon and to lock on the finger proximally of the knuckle when righted. It resists turning about the knuckle and is exteriorally configured to accommodate adjacent fingers, thereby suppressing discomfort due to pressure and rubbing against the adjacent fingers.

Abstract: The present shaft coupling is intended for releasably linking two or more vices to each other in a torque transmitting manner. The devices may, for example, be turbines each of which has a shaft. Two bearing mounts are provided for one of the shafts, but only one bearing mount is provided for the other shaft at its end remote from the coupling. The coupling between the two shafts is formed by inserting a non-circular end portion of one shaft in a corresponding non-circular aperture in the end of the other shaft. An axially extending bolt firmly clamps the two shafts together in the axial direction. One or both of the shafts may be hollow. The non-circular profiles of the shafts may be splined, or have a polygonal profile, and the polygonal profile may be tapered. A polygonal profile as used herein may be one with only three sides.

Abstract: A balance weight supported by a spring clip is inserted inside the low turbine shaft of a jet engine at the proper position and frictionally engages an inner bulkhead in the form of an "anti-oval plug". The clip is provided with a threaded opening to receive the threaded end of an elongated rod whereby the clip is inserted within the shaft and installed at the desired location after which the rod is unscrewed from the clip and withdrawn, leaving the weight in place on the anti-oval plug.

Abstract: A universal joint having two intermeshed rotatable assemblies in driving and driven relationship. Each of the assemblies of the joint has a base adapted to be connected to a rotatable device. Each assembly has a plurality of yoke arms fixed at one end to the base and at the other end to a joinder disc through which the axis of rotation of the base passes. Each of the yoke arms extends in a plane including the axis of rotation of the base and curves outwardly from its common point of joinder and then inwardly toward the axis of rotation of the base. Each yoke arm has an eliptical cross-section at its end attached to the base and gradually tapers to a circular cross-section toward its other end at its common point of attachment to the other yoke arms.

Abstract: Uniform load clutch device for transmitting a motion from a driving member to a driven member while permitting friction slippage between the two members should the driven member be stopped, wherein the driving member has a cylindrical part on which are freely mounted first and second friction pads with the driven member interposed therebetween, and resilient biasing means mounted on said cylindrical part and locked thereon in operational position exerting a force to bring into firm engagement said members and friction pads, whereby no relative movement will take place between said resilient biasing means and said driving member during the transmission of said motion.

Abstract: A safety sleeve shields the working members of a well tool wherein two shoulders come together to eliminate the possibility of workmen loosing a finger between the two shoulders.

Abstract: The present invention relates to a method of producing pile or plush goods or fabrics on circular knitting machines with plush hooks in the cylinder and latch needles in the dial and circular double knitting machines by means of pile hooks in a needle bed. Certain selected pile hooks are raised prior to the needles in order to prevent the fabric from raising with the needles while the pile hooks which are not selected for the formation of pile loops are retracted prior to the feeding of the pile yarn. Subsequent to the formation of the pile loops, the pile hooks are advanced into the loop forming position by the stitch cam until the needles move into an inactive position after the stitch formation, in order that the stitches are relieved (from tension) and withdrawn from the dial.

Abstract: A method for producing double knit fabric of a given gauge (usually fine gauge) with an inlay of a coarser gauge yarn on a knitting machine with two needle beds. One side of the fabric is formed of only relatively fine gauge yarn and the relatively coarser inlay yarn is confined to the other or surface side of the fabric. Selected needles in one of the needle beds are replaced by drive elements. The inlay yarn is laid in by an inlay wheel driven in synchronization with the needle bed by said drive elements.

Abstract: A loop-controlled slide needle for the forming of loops by a loop forming textile machine, comprising a shaft, a hook integral with one end of the shaft, the hook having a tapered free end, the shaft tapering in the plane of the hook at the juncture of the shaft and the hook, a longitudinal groove formed in the shaft, and a slide bar slidably mounted in the groove for movement between one position in which the slide bar closes the hook and another position in which the slide bar leaves the hook open, the slide bar having an end which faces the free end of the hook and which has a recess for receiving the tapered end of the hook when the hook is closed by the slide bar.

Abstract: A spool frame adapted for transmission of thread to a circular knitting machine comprising a framework subdivided into open section areas with each open section area provided with superposed tiers of semi-circular supporting elements on which are rotatably supported spool carrier elements. Thread guide means are arranged above the topmost semi-circular tier of spool carriers to control feed of the thread to the knitting machine.

Abstract: In a knitting machine positive feed device of the type comprising a rotatable roller having a bracket mounted for free pivotable motion adjacent the roller under the control of a pair of weighted arms which are attached to the bracket, the fixed yarn guides which are disposed adjacent the opposing ends of one of said arms are supplemented by an intervening movable yard guide which is weighted for movement under the influence of gravity to take up slack in the yarn caused by any overfeed from the roller. The movable yarn guide can also be associated with a stop-motion switching device operative to turn off the knitting machine if the yarn should break.

Abstract: A knitted undergarment as formed from a knitted blank made entirely by rotary knitting upon a circle of needles of a circular knitting machine by first knitting a seamless tubular elastic waist encircling turned welt upon all of the needles, then knitting a seamless tubular body section in continuation of the welt upon all of the needles, and then knitting spaced seamless nontubular front and rear narrowed panels in continuation of correspondingly spaced portions of the body section upon correspondingly spaced groups of the needles, the yarn being introduced to the needles for the knitting of each course of the panels and being cut and clamped after the knitting of each such course, so that each course of the narrowed panels is knit of a separate length of yarn. The knitted undergarment is completed by joining the terminal end portions of the panels. The narrowed edges of the spaced panels then delineate spaced leg openings therebetween.

Abstract: A sealing arrangement for use at the inlet and outlet of containers in which a pressure above or below atmospheric pressure prevails, especially for treating webs of textile material. The sealing arrangement comprises two endless belts respectively looped around two pairs of reversing rollers with the rollers of each pair spaced from each other so that straight belt sections are formed between the rollers of each pair of reversing rollers. The web of goods is passed between two adjacent straight belt sections, which respectively pertain to the two endless belts, and rim portions, and which seal the space surrounded by the belts and located between the rollers against the pressure surrounding the container.

Abstract: An improved liquid flow mechanical diverter valve of the stream interaction type is provided. The valve includes a housing having an inlet for receiving a flow of liquid from a liquid source, a pair of first channels communicating with the inlet, each having an exit port, an interaction chamber, a pair of converging second channels between the exit ports and the interaction chamber, three exit areas directed away from the interaction chamber and two flapper assemblies, each having a first portion large enough to seat against and cover a first channel exit port, a second portion at an angle to the first portion and rigidly secured thereto, a pivot at the junction of the first and second portions, the second portions being spaced from and directed toward each other.

Abstract: A padlock construction including a body having tine-receiving holes and a shackle having tines insertable in the holes, wherein the body is provided internally with tumbler pins shiftable into and out of intersecting relation with a tine to lock the latter, the padlock body having a slot affording end access to the tumblers to shift the latter out of tine-intersecting relation to open the lock.

Abstract: Improved internal tooling for a swaging apparatus for attaching fittings to tubing. The tooling includes a draw bolt having a head at one end adapted to be connected to actuating means such as a hydraulic cylinder at its opposite end. A straight cylindrical resilient expander sleeve is coaxially disposed on the draw bolt and is bracketed by a pair of split, circular, anti-extrusion rings located in mating seats formed in facing end surfaces of the draw bolt head and a seal bushing. The facing surfaces of the head and bushing are further configured to include a ramp surface extending between the surface of the draw bolt and split ring seats.

Abstract: An apparatus for forming corrugations of "zero" pitch in coaxial cable includes a takeup drum which pulls the coaxial cable through a three jaw chuck or head at a speed related to the rotation of the head. The head includes three forming dies and three synchronizing gears which cooperate with the forming dies to synchronize movement of the forming dies for movement about the cable. By causing the takeup drum to pull the cable through the head at a predetermined rate, the forming dies cut parallel corrugations or "zero" pitch grooves in the cable jacket.

Abstract: An apparatus for stretching sheet-metal strips includes several bending heads removably mounted between pairs of tension rollers, each bending head comprising a slender deflecting roller journaled in two end bearings and supported by heavier, shorter back-up rollers arrayed in two closely adjoining rows. The back-up rollers of each row have stud shafts cradled in V-shaped notches of a multiplicity of parallel webs transverse to their axis, the webs being integral with a common beam swingably mounted on a supporting frame. Oppositely notched retaining yokes are detachably secured to the webs to hold the roller shafts in place and to complement the notches to diamond-shaped seats for these shafts. The bearing notches of all the webs are simultaneously machined and/or trued by the same tool sweeping thereacross.

Abstract: A device for removing the press rest from the front side of a press disc for extruding tubes which has a substantially plane rear surface opposite the front side of the press disc. This disc comprises supporting means for supporting and holding the press disc from which is stripped a press rest. The device also comprises shearing means having a shearing surface which, when the press disc from which the press rest is to be stripped, rests on the supporting means, defines an obtuse angle with the rear surface of the disc. The disc and the shearing means are movable relative toward each other so as to cause the shearing means in response to such movement to strip the press rest off the press disc.

Abstract: A tool for shaping the end of a branch tube which is to be engaged in a socket in the side of a main tube which tool comprises a die having an aperture to neatly receive the end of a branch tube to be shaped, and an intersecting bore in which a pair of cutters are disposed to each extend into the aperture, the cutters each having slits into which the end of a branch tube may be inserted, the slits being shaped to notch out diametrically opposed segments from the branch tube against the die, means being provided to displace the cutters outwardly and to return them after displacement.

Abstract: A three-point, air-bending sheet metal bender comprising a pair of elongated U-shaped finger dies mounted parallel to one another is disclosed. The elongated finger dies are mirror images of one another (when appropriately aligned) and, prior to bending, are spaced from each other by an amount generally equal to the thickness of the sheet of metal to be bent. The elongated finger dies are laterally position adjustable such that the "finger" of one die is alignable with the "palm" of the other die and vice versa; i.e., the finger of each die is alignable with the palm of the other die. During bending, the "finger" die remains fixed and the "palm" die rotates. As the palm die rotates, sheet metal located between the two dies is bent. The direction of bending, with respect to the plane of the sheet of metal prior to bending, is determined by the die that is chosen to rotate.

Abstract: Removing the crust of oxide formed on the surface of a continuously casted copper bar by projecting a liquid (water or a rolling emulsion) under pressure of between 20 and 60 atmospheres against the periphery of the bar, the flow of the liquid under pressure being less than 50 liters/minute.

Abstract: A process for finishing a 15.degree. to 180.degree. pipe bend which has been preformed on a pipe bending press comprises submitting a preformed pipe bend at a temperature of 700.degree. to 900.degree. C. at which it leaves a pipe bending press to a hot sizing operation which includes trimming both ends of the pipe bend to precise dimensions to eliminate further finishing.

Abstract: This disclosure relates to a manifold for use in conjunction with a reciprocating die set for controlling air pressure within a sealed die which is closed by a formed shell so as to make certain that the shell remains with the sealed die as it is retracted relative to a die center, the manifold providing for a predetermined vacuum within the sealed die, which vacuum being sufficient to assure retraction of the formed shell with the sealed die but at the same time being maintained sufficiently low so as to prevent damage to the shell during the ejection thereof from the sealed die.

Abstract: A cupping tool for use in a double acting press to perform the operations of blanking, drawing and redrawing of sheet stock in predetermined timing sequence to form a cup during each stroke of the press and wherein the successive punching operations of telescoping, draw and redraw punches are governed by means of an automatic punch interlock means wholly enclosed within the body of the tool and actuated by relative movement of the draw punch and the tool body.

Abstract: A patenting process and a hot-forming process take place simultaneously, based on the principle of the direct electrical resistance heating, in an apparatus wherein the steel wire is led onto two discs or drums, provided with peripheral surfaces having different diameters and immersed in the patenting medium and from here the wire is led onto a guide disc or drums, outside the patenting medium.

Abstract: A method of forming a socket on a tube where a branch tube is to be joined to it, which consists of the steps of forming an aperture in the side of the tube which aperture is smaller than the internal dimension of the socket required, inserting expandible jaws into the aperture, placing a sliding former into contact with the tube around the jaws, and expanding the jaws while causing relative outward axial movement of the former in relation to the jaws.

Abstract: A device for use by plumbers and the like to compress the end of a length of hollow metal tubing such as a copper water pipe which has been expanded to a size greater than its normal diameter. The device allows such tubing to be compressed back to its normal diameter. A manually operable cam causes a hollow sleeve to move back and forth. The sleeve in turn causes a plurality of die members to move inwardly when the cam is activated. The sleeve is provided with a sloping inner surface and each of the plurality of die members is provided with a sloping outer surface having substantially the same angle of slope as the inner surface of the sleeve so that when the sleeve is moved by the cam, the plurality of die members will be uniformly forced inwardly to compress the end of a length of tubing inserted therebetween in a straight, uniform manner.

Abstract: A device for shaping the outer surface of a workpiece in which a sleeve is resiliently deformable in a radial direction. The sleeve is placed coaxially within a flywheel and removably fastened in a body member. A ring-shaped tool is coaxially located within the sleeve. The tool has at least five forming segments uniformly disposed on the circumference of the tool. The segments are integrally connected to one another by means of a neck portions which extend on at least one of the two axial sides of the tool. The tool is rotationally mounted in the body by means of an adjustment bushing. At least two rolls are located between the outer surfaces of the sleeve and the inner surface of the flywheel such that the rolls press the sleeve against the forming segments of the tool to deform the segments radially inwardly. The rolls are mounted in a cage which fixes their mutual angular positions.

Abstract: A wire connector crimping device including a base having a generally flat underside and provided on its upperside with a plurality of receivers for conformably receiving different size wire connectors to be crimped, a rocker pivotally mounted over the base and having a plurality of crimping formations for crimping relation with respective receivers, and limit means limiting the crimping formations to movement into their crimping relation with respective receivers.

Abstract: This invention relates to an automatic method and apparatus for quick and convenient testing of one or more geophones of a geophysical data acquisition system through the generation and analysis of the impulse response characteristics of such geophones. In particular, geophone response characteristics related to first and second adjacent absolute peak amplitudes associated with the damped equation of motion of the geophone coils are detected and digitally indicated in a surprisingly accurate manner, irrespective of whether or not the testing is carried out in a laboratory or field environment.

Abstract: A narrow banded acoustic transducer is driven by a VCFO whose output is varied by input signals of variable amplitude. One can simulate acoustic emissions for purposes of calibrating transducers which monitor a structural part for such emissions. Different signals for the control of the VCFO are generated to provide for specific test pulses.