Abstract: A resistor trimming method includes the steps of: forming a first slit from an edge of a resistor interconnecting first and second electrodes provided on an insulating substrate in the proximity of and parallel to the first electrode; forming a second slit as a continuation of the first slit toward to the second electrode perpendicularly to the first slit; forming a third slit from a point of the edge of the resistor and parallel to the first electrode, the point being shifted from the first slit toward the second electrode, the third slit having a greater length than the first slit in a direction along the first electrode; and forming a fourth slit as a continuation of the third slit toward to the second electrodes perpendicularly to the first slit.

Abstract: In accordance with the present invention, trim pads used in trimming on-chip resistive elements are formed in the scribe channels interposed between respective dice on a wafer. Metal traces connect the trim pads to their associated resistive elements formed on the dice. Thus, each trim pad formed within the scribe channels results in a corresponding increase in the usable silicon surface area of the dice, thereby saving valuable silicon real estate.

Abstract: Microwave apparatus, such as microwave power dividers or combiners, having an adjustable terminating resistor. The present invention allows adjusting or trimming of the resistor and pretesting of substrates on which the apparatus is formed prior to installation of expensive integrated circuit components. The microwave power divider or combiner has a central contact disposed at a midpoint of the terminating resistor. This central contact is thus disposed at the midpoint of the terminating resistor and is coupled to a test point. Outer edges of the central contact are constructed to be parallel to inner edges of impedance paths or traces over which the terminating resistor lies so that each section of the terminating resistor has substantially the same resistance value.

Abstract: The present invention involves adding additional structures to a polysilicon resistor which do not significantly affect the resistance of the polysilicon resistor. These additional structures add to the area of the polysilicon resistor, and therefore reduce the self-induced temperature change caused by the voltage across the resistor. Since the resistance of the polysilicon resistor depends on its temperature, the reduction of the self-induced temperature change lowers the variation in the resistance value at different voltages.

Abstract: A lightning surge resistor network includes a ceramic substrate and a thick-film resistor deposited onto the substrate. To prevent material spatter and to contain and isolate any arcing that can occur in the event the thick-film resistor opens during a severe over voltage condition, a ceramic cover is mounted over the thick-film resistor. The thick-film resistor is thus fully contained between the ceramic substrate and the ceramic cover. Preferably, the ceramic cover is adhered to the ceramic substrate by means of an adhesive film deposited onto either the cover or the substrate adjacent the outer periphery of the cover. Preferably, the mount of adhesive is reduced at preselected locations along the outer periphery of the cover to form weakened areas in the seal between the cover and the substrate. The weakened areas permit gasses to escape in a predetermined direction in the event excessive pressures are formed under the cover when the thick-film resistor opens under an over voltage condition.

Abstract: A thermistor type temperature sensor having a substrate made from an electrically insulating ceramic plate. A thin or thick film detecting resistor is printed on the substratum. A thick or thin film pull-up resistor may also be printed on the substratum, and trimming of the resistors is possible. The ratio of B-constant values for the detecting resistor and the pull-up resistor may be selected so that it is locate between 0.4 to 0.9 or 1.1 to 1.5. The detecting resistor may be constructed from thermistor sections of the same composition and the sections may be connected in parallel or in series. The thermistor sensor can be connected to the pipe through which a gas passes. When the sensor is connected to the pipe, the angle of the measuring plane may be adjusted, so that a precise measurement can be obtained.

Abstract: The present invention concerns a thermal recording apparatus, preferably an ink jet thermal recording device and, a process for forming the same and, accomplishes uniformized heat energy action of the heat acting surface (a protective layer surface when there is protective layer), namely the heat-generating resistors of a plurality of electrothermal transducers. The present invention has uniformized the amount of heat energy generated during recording at the heat acting portions by positively changing the shape or the thickness of the resistors concerned with the heat acing portions or/and the constitution itself of the protective layer depending on its existing position.

Abstract: A thick film circuit board includes a substrate, a thick film resistor on the substrate and having a trimming region and a protecting element on the substrate for protecting the thick film resistor and having a window through which the trimming region is exposed. The protecting element may be a protective coating disposed on the substrate. Alternatively, the protective element may be a protective frame extending along an external periphery of a region where the thick film resistor is located on the substrate and having a height for protecting the thick film resistor from mechanical damage.

Abstract: A chip resistor is provided which comprises an insulating chip substrate, a resistor element formed on the chip substrate, a first pair of electrode terminals branching out from one end of the resistor element, and a second pair of electrode terminals branching out from the other end of the resistor element. One of the first pair electrode terminals is a current terminal while the other of the first pair electrode terminals is a voltage terminal. Similarly, one of the second pair electrode terminals is a current terminal, and the other of the second pair electrode terminals is a voltage terminal.

Abstract: An electronic probe circuit having ac and dc amplifiers and an input compensation subcircuit is enclosed within a trim housing that replicates the electrical effect of the probe housing. The circuit is laser trimmed through ports in the trim housing. The difference between the voltage at 80 nsec and 1.4 .mu.sec points on a step voltage provides a first calibration factor while the difference between the 3 nsec voltage and the 80 nsec voltage provides a second calibration factor. A resistor in the DC amplifier is trimmed to an absolute voltage with a step scan laser cut. A resistor in the AC amplifier is trimmed with a laser L-cut until the difference between the 80 nsec and 1.4 .mu.sec points of the step voltage equals the first calibration factor. A capacitor in the input compensation subcircuit is trimmed until the voltage difference between the 3 nsec and 80 nsec points equals the second calibration factor.

Abstract: An electrode of a conductive material containing silver and a thick-film resistor of an electric resistive material containing cermet, which is electrically connected to the electrode, are formed on an electric insulating substrate by printing respectively. Then, the thick-film resistor is directly irradiated with a laser beam to be trimmed, and thereafter a protective film of an electric insulating material containing resin is formed on the insulating substrate by printing, to cover the electrode and the thick-film resistor.

Abstract: A collinear terminated transmission line structure and method for producing same is presented. The structure comprises a plurality of conductors electrically connected to a plurality of resistors. A predetermined spacing between each of the plurality of conductors ranges from 2 mils to 7 mils. Greater spacings are easily accomplished with the present method. The method comprises the steps of screen-printing a resistor swath onto a substrate, the swath being adjacent to one end of the plurality of conductors. After the substrate is dipped into a solution, the resistor swath is laser trimmed to form the plurality of resistors. The substrate is then rinsed with warm water to remove the solution. The solution can be a poly-vinyl alcohol and isopropyl alcohol mixture.

Abstract: Several trim patterns are illustrated which are suited for use in high voltage, surge prone environments. The invention combines a block resistor with a simple scan cut and two or more plunge cuts to simply form a resistor. The resulting resistor is immune to adverse affects associated with current crowding and arcing, both known to have much adverse impact on the prior art.

Abstract: A semiconductor device includes a resistor network having a plurality of trimming polysilicon resistors. The polysilicon resistors have the same width and different lengths and can be selectively fused according to the value of current which is caused to flow therein. The resultant resistance of the resistor network is changed by selectively fusing the polysilicon resistors. The output characteristic of the semiconductor device can be adjusted by changing the resultant resistance.

Abstract: A resistive body of a hybrid integrated circuit has a resistance pattern on a resin film. Bonding pads permit connection of current through the resistance pattern. The resistance pattern may form part of a detecting bridge for overcurrent detection. One embodiment of the invention uses a rectangular resistance pattern with an opening in the center to force current to flow on a perimeter path for minimizing maximum temperature. Another embodiment uses a serpentine resistance pattern. A face-down resistance patter reduces interference. A direct-connection bonding pad reduces the voltage generated in a parasitic capacitance to improve the resistance of the resin film to voltage breakdown.

Abstract: A resistor structure (10) having a heating element (35) and a resistor (32), and a method of trimming the resistor (32). The heating element (35) is separated from the resistor (32) by a layer of dielectric material (19). The resistor (32) has a layer of resistive material (23) on an etch control layer (22). The resistor (32) is trimmed by providing current pulses (62) through the heating element (35). Heat generated by the current pulses flows to the resistor (32) and anneals or trims the resistor (32). A resistor trimming variable, e.g. a voltage across resistor contacts (30, 31), is monitored and the current pulses are modulated in accordance with the value of the resistor trimming variable (63). The trimming step is terminated when the desired resistance value of the resistor (32) is attained.

Abstract: An electric tool rheostatic device in a switching arrangement is provided for regulating the speed of an electric motor in an electric tool. A circuit board for receiving electronic components is disposed in a switch housing. A potentiometer disposed within the switch housing includes a potentiometer slider operatively connected with a manually-operated actuating member and a resistance track that is constituted by a chip resistance element produced independently of the circuit board according to surface mounted device technology and mounted on the circuit board independently of the potentiometer slider. Upon assembly of the switching arrangement the potentiometer slide is adjustably located on the resistance track by the manually-operated actuating member for controlling resistance.

Abstract: An electronic probe circuit having ac and dc amplifiers and an input compensation subcircuit is enclosed within a trim housing that replicates the electrical effect of the probe housing. The circuit is laser trimmed through ports in the trim housing. The difference between the voltage at 80 nsec and 1.4 .mu.sec points on a step voltage provides a first calibration factor while the difference between the 3 nsec voltage and the 80 nsec voltage provides a second calibration factor. A resistor in the DC amplifier is trimmed to an absolute voltage with a step scan laser cut. A resistor in the AC amplifier is trimmed with a laser L-cut until the difference between the 80 nsec and 1.4 .mu.sec points of the step voltage equals the first calibration factor. A capacitor in the input compensation subcircuit is trimmed until the voltage difference between the 3 nsec and 80 nsec points equals the second calibration factor.

Abstract: A method for producing opto-electronic devices, such as opto-mechanical mouse devices, which includes adjusting a detector signal after a detector and emitter are connected to the remaining circuitry associated with the opto-electronic device. The method also includes a rough adjustment step wherein a the detector signal is adjusted to a predetermined output voltage, and a fine adjustment step wherein an encoder is rotated between the emitter and the detector, and the circuit is adjusted such that the duty cycle of a comparator is within a desired range.

Abstract: A trimmable resistor which is prepared with additional electrical contacts between the resistor and the substrate. These contacts are usually not connected electrically to the electronic circuit. Moreover, they do not extend across the entire width of the resistor. If the resistor is over trimmed, its resistance can be reduced by wire bonding a selected one of the additional electrical contacts to an end contact of the resistor. Multiple contacts may be placed along the substrate, both on the side of the resistor where trimming is to take place and on an opposite side.

Abstract: A fuse resistor protects a circuit from a surge, an overcurrent from an unexpected connection, or the like. When a continuous overvoltage higher than a predetermined value is applied to the circuit, the heat from a heat-generating resistant film fractures an insulating substrate of the fuse resistor to open the circuit. Changing the minimum current to which the fuse resistor responds, by modifying a cutout or notch on the substrate, makes it possible to use the fuse resistor anywhere in the circuit. A discharging-type surge absorbing element with a security mechanism that includes the fuse resistor can thus provide protection against a surge or a continuous overcurrent that is more than the rated value of the fuse resistor.

Abstract: A resistor ladder (10) includes a plurality of series resistors (16,18,20,22,24,26,28) connected in series with each other between a first terminal (12) and a second terminal (14). A plurality of shunt resistors (60,62,64,66, 68,70) are connected between junctions (48,50,52,54,56) of adjacent series resistors and the second terminal (14). The series resistors (16,18,20,22,24,26,28) and shunt resistors (60,62,64,66,68,70) are formed on a substrate (80) as film resistors which blow open at a predetermined current density. The shunt resistors (60,62,64,66,68,70) have a smaller cross-sectional area than the series resistors (16,18,20,22,24,26,28) such that they successively blow open from the first terminal (12) toward the second terminal (14), while the series resistors (16,18,20,22,24,26,28) do not blow open, as a progressively increasing voltage is applied between the first terminal (12) and the second terminal (14).

Abstract: To provide a chip resistor with small variation of ESD required when in automobile use, a chip resistor containing(1) insulating substrate,(2) a pair of terminations disposed over said substrate,(3) resistor layer of thick film resistor composition comprising a mixture of finely divided of conductive component and glass binder,wherein said resistor layer being disposed and patterned on the surface of said substrate by printing and firing to form continuous conductive path comprising divided sections connecting to each of said termination, and divided section angled in its longitudinal direction from the direction of current flow in said respective 4 sections connected to said terminations being insulated and separated from one another by underlaying substrata resulting into considerably longer resistor geometry than distance between said terminations.

Abstract: When resistor elements, common electrodes and individual electrodes are formed on a substrate, a disconnected portion, i.e., open portion is formed in one of the common electrodes. After the respective resistor elements are trimmed, the disconnected portion of the one common electrode is bridged by a conductor.

Abstract: A hybrid resistance card (R-Card) is manufactured using a two-step process wherein an electrically conductive ink layer and an electrically resistive ink layer are printed onto a surface, which may be either a substrate or the part on which the R-Card is to be used. The conductive ink layer is selectively applied in a pattern of shapes to electrically short out portions of the resistive ink layer, thereby permitting the R-Card to have a predetermined resistive taper across its width according to a desired resistivity curve. The resistive ink layer comprises grid-like lines bordering and separating the conductive shapes. The resistive taper is substantially continuous along the length of the R-Card, at least linearly, though if the card is designed to cover an entire part, it is substantially continuous along a plurality of directions on the card, with the tapers being designed to round into one another.

Abstract: Thin or thick film resistor devices (e.g., electronic resistors and thermistors) are trimmable without disturbing the active resistor film or necessarily requiring temperature control during trimming by providing a plurality of electrically conductive fingers having one end integral with one of the electrodes and a terminal end which extends at least substantially across the cross-wise dimension of the resistance film. The electrode fingers thereby electrically bridge a respective surface region of the substrate on which the electrodes and film are disposed. One or more of these fingers may thus be severed from the electrodes at the bridged respective surface region of the substrate so that the resistance value of the device can be controllably selected.

Abstract: An on-board oil quality sensor for use in an internal combustion engine formed of a pair of resisitve elements mounted on a common substrate, wherein one of the resistive elements is exposed to the oil for corrosion as the oil contaminants increase and the other resistive element is protectively sealed from the oil contaminants. Both resistive elements are exposed to the oil temperature and are suitable for monitoring by a bridge type circuit to determine the level of corrosive contaminants in the oil.

Abstract: A thin film resistor with an insulating layer disposed between a substrate material and a resistor material is disclosed. Also, disclosed is a technique for fabricating this thin film resistor. In accordance with the preferred embodiment, the thin film resistor employs an insulating layer of silicon nitride with a thickness of 2000 .ANG.. The insulating layer prevents the resistor layer from diffusing into the substrate material which, in turn, significantly reduces variations in the resistor value during accelerated life testing. Compared to thin film resistors with a resistor layer evaporated directly upon a substrate material, reliability is increased from a few hundred hours up to thousands of hours. Also, the maximum current handling capability is increased by greater than one order of magnitude, which results in a thin film resistor which requires less surface area of a wafer.

Abstract: A trimmable resistor is provided which can be trimmed with a single movement of a laser beam without requiring intermitted deenergizations of the beam accompanied by measurements of the resistance to determine additional material removal steps. The procedure of the present invention begins the material removal at a location within the body of the resistor and displaced from all edges of the resistor body by a predetermined amount. The energization of the laser immediately begins to remove material at its initial location and, as the laser is moved to a second location, a single cut is made to calibrate the resistor wherein the entire cut is located within the body of the resistor and no part of the cut intersects any edge of the resistor body.

Abstract: A blower motor speed control resistor array in which the resistor elements contain an electrically conductive plastic material which melts to limit the blower motor current in the event of an extreme temperature condition. The conductive plastic is insert molded on a terminal array to form a self-supporting structure adapted to be disposed in an air duct. Each resistor of the array is defined by a number of legs of electrically conductive plastic extending between a pair of parallel headers, in the manner of a picket fence.

Abstract: A low noise miniature potentiometer utilizes thick film deposits of resistive material which extend adjacent to deposits of conductive material. The conductive region is sliced into a plurality of spaced-apart conductive elements. Electrical paths through resistive elements can be lengthen by laser trimming of the resistive material thereby providing for very precise incremental resistances between pairs of spaced apart conductive elements. If desired, an increased range of resistivity can be achieved by utilizing a second deposited thick film region extending along the conductive region and in contact therewith. Laser trimming can be used to increase conductive path lengths in the second resistive element thereby providing a broader range of resistance values.

Abstract: A trimmable resistor network including a plurality of series-connected sections each including a plurality of paralleled link resistors each capable of being cut so as to be eliminated from the network, the paralleled resistors in each section having resistance values such that the section resistance changes by at least approximately integral multiples of a fixed amount when the resistors are cut.

Abstract: Disbonded two-level (bimetal) metal interconnections are removed by first vaporizing metal in the lower level that is exposed by the narrower metal on the upper level using a pulsed laser beam having an energy density above a vaporization threshold in a first beam width and then vaporizing the remaining portion of the metal in both levels using the laser beam with a narrower beam width that covers only the narrower width of the upper level metal.

Abstract: A process of fabricating an electrical resistor and a product produced thereby in which trimming of a resistive element of a material exhibiting thermosetting properties is accomplished by in-situ annealing of one or more regions across the width of the resistive element to certain predetermined temperatures, thereby altering the crystal properties and the sheet resistance within those regions. Annealing is preferably done by laser radiation at levels below that at which any cutting or ablation of the resistive element will occur, thus avoiding defects in the resistor or associated circuits. By controlling laser radiation and the annealing process, virtually any desired trim slope may be obtained, resulting in improved trimming accuracy. Efficiency of the process is enhanced by annealing the resistive element to obtain compound trim slopes corresponding to coarse and fine trimming of the resistive element.

Abstract: A hybrid substrate comprises an aluminum-based ceramic base substrate and a silicon layer provided on the base substrate.

Abstract: A current shunt for converting a current to a voltage. The current shunt of the invention is made from a conductive material such as a high performance resistance alloy in sheet form which is sheared, punched, and bent to produce a highly stable current shunt with respect to time and temperature. Contact pins of current and potential connections are welded to the material using a fusion welding process, and techniques are also provided for isolating the potential contacts from the current contacts so as to improve stability. Trimming slits of the type used for thin film or foil resistors are also extended to bulk materials in accordance with the invention such that highly accurate resistances may be obtained. An integral heat sink and strain relief mechanism is also provided so as to minimize the adverse effects of temperature on the resistance of the material. The resulting current shunt has an extremely stable resistance value with respect to time and temperature at a minimal cost.

Abstract: An electrical resistor which is fabricated from traces of resistive material on a substrate of insulating material. The traces are interconnected electrically in series by first links and in parallel by second alternating links, which are connected to different terminals on the substrate. The second links are cut, preferably by laser trimming, so as to select the value of resistance of the resistor by reducing the number of traces connected in parallel and increasing the number of traces connected in series. Where the resistance of each trace is "R", the value of the resistance is adjustable by severing the second links from R/n to nR, where n is the number of traces.

Abstract: An intermediate product is provided and includes a substrate having at least one thick-film circuit formed thereon. An outer surface of a first portion of the thick-film circuit is coated with a readily removable protective material such as ethyl cellulose to protect the first portion from hot-slag substrate material generated during a laser scribing operation. The substrate also includes at least one uncoated portion which can be laser scribed for separation of the thick-film circuit from the remainder of the substrate. After laster scribing, the protective material is removed to permit visual inspection of the thick-film circuit.

Abstract: A trimmed resistor is provided which has no directional feature when used and is easily mounted on a printed base board. In the trimmed resistor, there are formed four external electrodes arranged at peripheral portions of a rectangular insulation base plate in a point symmetrical distribution about a center of the insulation base plate, a film-like resistance body connected with all of the external electrodes, and a protective film covering the film-like resistance body. Two electrodes among the above-mentioned four electrodes are used as resistor terminals, and a cut slit for trimming is formed in the resistance body longitudinally or as starting from a side of the electrodes serving as resistor terminals.

Abstract: A flat resistance for a blower control unit of an automobile air conditioner, and a blower control unit using the same. The flat resistance includes: a porcelain enameled metallic substrate including a flat head portion, having an edge and one surface, and parallel terminal supporting portions projecting outwardly from the edge of the head; a resistance circuit printed on the one surface of the head portion, the resistance circuit including a plurality of resistances electrically connected in series; a temperature fuse, interposed in the resistance circuit, for being tripped to break the resistance circuit when the porcelain enameled metallic substrate becomes overheated; and terminals, printed on both the head portion and the terminal supporting portions, each terminal being connected to one end of a corresponding one of the resistances.

Abstract: Conductive material is applied to a resistor to provide controlled shunting of current from localized regions of the resistor that would otherwise destructively fail during surge. Various embodiments are disclosed having varying resistance, dimension and placement. The continuity of the original resistor material is not altered, nor is the current diverted in such as way as to create a new localized regions that might destructively fail. The resistors so designed have application in lightning surge environments, power supply and power input circuitry and other applications where potential short duration surges might otherwise cause destructive failure of standard resistors.

Abstract: A heater comprises a substrate and an electrically conductive heating section having branched portions on its lateral edge. The heating section has notches at those portions of its lateral edges that are opposite to the branched portions. The notches increase electric resistance of the heating section at the branched portions to enhance heat generation of the heating section at the branched so that the heating section is heated at a predetermined temperature over the entire length of a transfer paper sheet.

Abstract: A capacitor which includes a dielectric layer, a metal electrode and a capacity adjusting electrode erodable by exposure to light energy, the capacity adjusting electrode being a film made of at least one selected from metallic oxides, metallic nitride and metallic boride.

Abstract: The present invention relates generally to a new method of repairing electrical lines, and more praticularly to repairing electrical lines having an open at the module level with devices in place. Various methods and processes are used to repair this open or defective portion in an electrical conductor line. It could be repaired by securing a jumper wire or nugget across the open or the repair could be made by a deposition process, which includes but is not limited to filling the open with a solder type material or inserting a solder coated electrical wire and heating the solder and allowing the solder to melt and repair the open. One of the attributes of this invention is the ability to repair on a substrate or module on which active components such as chips, and passive components such as pins, capacitors, etc. have been attached. The invention also allows repair of fine line patterns which are normally not repairable by conventional techniques.

Abstract: A precision thick film resistor has a deposited thick film conducting layer which is adjacent to and in contact with a deposited thick film resistive layer. A laser scribed line, having a width on the order of 2 mils, separates the conductive region into two parts and then extends into the resistive layer. The value of the resistor is set based on the extent that the line extends into the resistive layer. A plurality of thick film conducting elements can be formed by depositing a continuously extending thick film conducting layer on a substrate. Laser scribed lines can be used to isolate various conducting elements in the deposited film from one another. Elements are separated from one another by 2 mil wide laser scribed lines.

Abstract: A digitizer screen and method of making. A coated conductive plastic film is perforated and is used in conjunction with a glass or other panel to provide a screen which may be used in an electronic digitizer for converting the position and movement of a stylus or other device on the screen to electrical signals representative of such positioning and movement. The perforated coated conductive plastic film may be laminated to the glass panel to form an integrated structure which does not require the use of masking and etching or similar processes to produce a desired apertured matrix pattern in the plastic film. Various arrangements of the plastic film are disclosed which facilitate the connection of the apertured portion of the plastic film to associated electronic components.

Abstract: A hybrid substrate comprises an aluminum-based ceramic base substrate and a silicon layer provided on the base substrate.

Abstract: An improved heaterboard, and method and apparatus for producing same is disclosed herein. A foil layer is bonded to a paperboard substrate and a circuit path is cut in the foil layer to define a heating circuit. In a preferred method, the circuit is defined by cut scores and short-circuiting across the cut scores is prevented by a reverse scoring operation in which the circuit pattern is scored in the surface of the heaterboard opposite the surface having the foil heating layer thereon. Various heaterboard circuit patterns and an apparatus for forming heaterboards are also disclosed.

Abstract: An artificial resistive card which prevents scattering due to diffraction, and which forms impedance transitions from ground planes to antenna apertures or to free spaces, incorporates resistive and conductive layers formed on a substrate. The conductive layer is etched away, either partially or entirely, using integrated circuit technology in order to vary the resistivity of the resistive card. Portions of the resistive layer may also be etched away to expose the underlaying substrate and increase the resistivity of the resistive card. The size and dimension of the resistive and conductive pattern left after etching determines the value of the resistivity and is easily and accurately reproduced.

Abstract: A generic chip carrier is described which includes, as integral parts, a voltage bus and a plurality of terminating resistors connected between the voltage bus and signal traces on the carrier. The voltage bus wraps around the chip carrier, thus providing a large area of metal. Through the selective use of the terminating resistors, the generic carrier can be customized for a particular type of integrated circuit, i.e., source or destination termination of signals. A signal trace may be customized by "operating" the terminating resistor with a current spike applied by a standard electrical probe. Spare bonding pads and terminating resistors are placed at intervals about the periphery of the carrier as insurance against defective or mistakenly removed terminating resistors.