Abstract: A simplified master controller or outguard circuit monitors and controls a plurality of separate slave, or inguard, circuits. Only a single watchdog circuit is provided on the outguard arrangement, with simplified timers being provided on each inguard arrangement to generate a direct hardware reset signal for local microprocessors in the inguard circuits using existing serial communication lines. A break signal generated by the watchdog in the outguard circuit is detected and, without interpretation, converted to the reset signal for the inguard circuit in synchronism with operation of the outguard circuit.

Abstract: For circuitry having analog and digital circuit sections and a signal flow path therebetween, a guard crossing for establishing electrical isolation and virtually no capacitive coupling between the two sections comprises optical fiber cables extending between circuit boards or between partitioned regions of a common circuit board carrying the analog and digital section for interfacing signals therebetween. Electrooptical transmitters and receivers in each section are coupled to the optical fiber cables. In accordance with one embodiment, bit serial signals are transmitted between the analog and digital sections through a single optical fiber cable for each direction. In another embodiment, a plurality of optical fiber cables for each direction carry the parallel bits of bit parallel signals between the two sections.

Abstract: A battery charger supplies to a battery an output voltage having a desired temperature coefficient of voltage. The charger includes an operational amplifier having a summing junction to which a reference current and a feedback signal derived from the amplifier output are supplied. The V.sub.be multiplier circuit includes a bipolar transistor which is biased into its active region so that the charging voltage supplied by the amplifier is temperature corrected in accordance with a negative coefficient of voltage characteristic of the transistor.

Abstract: A hybrid circuit structure includes an electrical circuit and a heating circuit therefor, both mounted on a single substrate. Valuable substrate space is saved by mounting the electrical circuit components on one surface of the substrate and the heating circuit elements on the opposite surface. A temperature control circuit is included, preferably mounted on the same surface as the electrical circuit components. Precision resistors for gain control and other functions may be provided on a separate substrate which may be mounted directly to the single substrate or to a separator therebetween. The precision resistors are in thermal contact with the temperature controlled heating circuit, thereby further increasing the stability of the circuit.

Abstract: The calibrator of an ohmmeter is compensated to eliminate any error as a result of the resistance of leads interconnecting terminals of the ohmmeter and a reference resistance to which the ohmmeter is connected during calibration. In accordance with one aspect of the invention, ohmmeter current flowing through a buffer amplifier biased by a floating power supply bypasses the ohmmeter leads. In accordance with another aspect, a current equal in magnitude but opposite in direction to the ohmmeter current is applied to the leads.

Abstract: Method and apparatus for the regulation of a modulated signal transmitted from a transmitter (E) to a receiver (R) in a differential protection system for an electrical installation. The invention lies in the regulation of the frequency spectrum of the modulated received signal (SMR). The presence of a fault in the electrical installation in this spectrum of low frequency components is attributed to presence of noise bursts in transmission affecting the received signal (SMR).

Abstract: In a temperature measurement system using a thermocouple connected to a pair of circuit wires coupled to a voltmeter for providing an output reading, an isothermal block (48) formed of alumina ceramic contains a series of openings (58-66) in linear juxtaposition. Metal connectors (68) located in two of the openings to interconnect the thermocouple and printed circuit wires of a circuit board (52) establish a reference junction. A temperature sensor (50), preferably a transistor, in a third opening measures the temperature of the isothermal block (48) to compensate the output reading for error created by the reference junction. The connectors (68) are in resilient contact with the interior wall of the isothermal block (48) to maintain good heat conductivity between the connectors and the temperature sensor (50). Portions of the connectors (68) extending outside the isothermal block (48) retain the isothermal block (48) to the circuit board (52).

Abstract: A test clip and grounding adapter assembly comprises a conventional integrated circuit test clip of a type having parallel arrays of signal conductors retained in a pair of molded plastic arms biased closed on the leads of a unit under test.An adaptor in accordance with the invention having twice as many conductors as the test clip interconnects the test clip and a ribbon cable. The additional conductors within the adaptor interposed with the signal conductors in the clip are grounded to electrically shield the signal wires.

Abstract: Random bits are written successively into the cells of a random access memory (RAM) system, then complemented, through a first sequence of cell addresses distributed substantially uniformly throughout all the cells of the memory. Through an opposite address sequence, the contents of the cells are read and then complemented. Finally, through the initial sequence of cell addresses, the contents of the cells are again read. Differences between read and expected cell contents identify memory cell faults. The random bits preferably are generated by a softward implemented, reversible pseudorandom sequence generator, and the uniform address sequence is generated by an address hasher programmed with an address function that exercises all address lines essentially equally.

Abstract: Circuit faults in an electronic system are isolated by a programmed computer that guides a technician node-by-node on a unit under test (UUT), such as a circuit board, to the source of a failure. Stimulus pattern signals are applied to the circuit, and responses at the circuit nodes are made by a measurement probe under the hand of the technician. As each node is probed, a stimulus pattern signal tailored for testing that node is applied to the UUT. The measured response is compared to a predetermined response corresponding to an operational UUT to generate a failure accusation or recommend the next node to be probed. The computer is programmed to expedite the search for the source of the failure by displaying to the technician clues which define the circuit nodes most apt to be defective as a result of preliminary functional testing of the UUT.

Abstract: To eliminate crosstalk between successive measurements of an integrating analog-to-digital converter having MOS linear amplifiers (16) that as a result of ion distribution shift in its input devices gate oxide (24) tends to retain a conversion residue (R), at least one "dummy" conversion cycle (38) is executed prior to each input signal measurement. The "dummy" conversion cycle (38) reduces the residue (R) by moving input gate ions into stable positions corresponding to the magnitude of the input signal to be next measured.

Abstract: A test voltage is applied through an array of "guarded" switches (58) to selected ones of a plurality of components to be measured. Each switch (58) comprises first and second input terminals (69, 72), first and second output terminals (70, 74), and a wire (76) interconnecting the second input and second output terminals (72, 74). The switch (58) is operable selectively in a first state interconnecting its first input and output terminals (69, 70) and in a second state interconnecting the second input and output terminals (72, 74). A buffer amplifier (88) couples the input signal from the first input terminal (69) to the wire (76) interconnecting the second and output terminals (72, 74) of the switch (58) as a "guard voltage" to prevent loading of the input signal by leakage resistances within the switch.

Abstract: A thermal link provides a thermal path between a heat source and a heat sink which compensates for irregularities on the surface of the heat source and/or heat sink and/or nonuniformity in the spacing therebetween. One embodiment utilizes a spring metal device having a free arm which allows the link to align itself under low pressure so that it is in intimate contact with both the heat source and heat sink. Another embodiment utilizes an elastomeric material filled with thermally conducting particles to form a mat that has a plurality of raised sections having air spaces between each of the sections. The raised areas deform under low pressure by expanding laterally into the air spaces to conform to the space between the heat source and the heat sink.

Abstract: To energize an electromagnetic clutch or other electromagnetic device having a movable armature, a voltage is applied across the coil of the device to cause an initial current to flow therethrough. A current dip upon initial movement of the armature is detected, and in response, a substantially linearly increasing current is applied to the coil, establishing a controlled movement of the armature.

Abstract: The storage units and the output of an averaging type recursive or non-recursive digital filter are modified by input signal changes greater than a predetermined amount indicative of a step change to provide a rapid step response characteristic.

Abstract: A method of making a molded circuit board includes forming a polymer base with a channel and an intersecting through-hole. The base is conductively coated by means of vacuum deposition to establish a circuit line. After the conductive coating is removed everywhere except the channel and the through-hole, a further conductive material is provided on the coating. The base is subsequently stress relieved and planarized.

Abstract: In a dual slope analog to digital converter, the input amplifier has an input selectively connectable to an unknown analog source or a known opposite polarity analog source. The output of the amplifier is directly or indirectly connectable to its other input to change the gain of the output. A microprocessor controls the converter to sequentially connect the unknown analog source, instantaneously change the output connection to change gain where appropriate, and connect the known analog source.

Abstract: A regulated voltage supply (10) for delivering a substantially constant voltage to a load (12) having a regulator (24) for controlling a raw voltage supply (22) to deliver that constant potential, wherein the supply includes sense leads (28 and 30) between the load and the regulator for monitoring load voltage, provided with a sense current cancellation circuit (30) for nulling sense current and preventing it from flowing through the sense leads; in a preferred implementation, including voltage-to-current converters (42 and 44) bridging respectively the output terminals (14 and 16) and the sense terminals (32 and 34), it provides a cancellation current equal in magnitude and opposite in direction to the sense current.

Abstract: The ladder network of a recirculation of remainder analog to digital converter has a voltage source that is regulated by a transistor and Zener diode together with feedback circuitry responsive to the regulated output voltage. Current through the circuit is controlled by feedback to establish equal and opposite temperature coefficients in the transistor and Zener diode of the regulator. The temperature stabilized voltage regulator produced thereby eliminates any requirement for trimmer potentiometers.