Abstract: An integrated circuit package has multiple integrated circuits (ICs) mounted face down directly on one surface of a flexible circuit which is disposed in an opening of a rigid signal carrier, such as a pin grid array. The flexible circuit provides connections among the ICs, and also between the ICs and the signal carrier via wirebonds. The flexible circuit is attached to a rigid support ring that is bonded to the signal carrier adjacent to the opening. A thermally conductive lid covers the opening and contacts the backs of the ICs for heat removal. A rigid plate presses elastomeric pads against the other surface of the flexible circuit to maintain firm contact between the flexible circuit and the ICs and also between the ICs and the lid. The package may be hermetically sealed by attaching a cover to the support ring.

Abstract: A process and a circuit are described for detecting collisions between packets being transmitted over a network and signaling the detection of collisions. Peak-detection is used to facilitate the detection of collisions. Embodiments of the process and circuit may also include the detection and signaling of packet transmissions by a transceiver coupled to the network. In a preferred embodiment, the detection of collisions and transmissions are signaled by the lighting of a corresponding light-emitting diode for at least a minimum duration.

Abstract: In a circuit design synthesis procedure in which the pointers are added to the data base to permit a path through the circuit to be followed, a qualified object is defined to be a data object that permits access expressed by a sequence (or chain) of access forms strung together. A mechanism is defined that permits access of any object in a logic design database relative to any other object in the data base. Access forms are strung together in a given format. This structure provides an easily understandable access form and it is defined in the rule grammar. This access form can be parsed in the synthesis procedure into a nest of (LISP) program functions, which, when evaluated, will return an object in the data base. This access chain is used in the antecedent and consequence portions of the rule structure for the purpose of modifying the target objects. This access structure permits the synthesis rules to make decisions on such parameters as timing, cell size, power, wire loading, model names, etc.

Abstract: A technique for issuing and revoking user certificates of authenticity in a public key cryptography system, wherein certificates do not need expiration dates, and the inconvenience and overhead associated with routine certificate renewals are minimized or avoided entirely. A Certification Authority issues certificates as required, and issues a blacklist having a start date, an expiration date, and an entry for every invalid certificate issued after the start date. Users assume that every certificate issued prior to the blacklist start date is invalid, and that invalid certificates issued after the start date will be included in the current blacklist. A new blacklist is issued prior to expiration of the current one, and the blacklist start date is changed only when the blacklist becomes unmanageably long.

Abstract: A purging station selected for removal of no-owner frames in a token ring network, and a corresponding method for its operation. The purging station initiates a purge cycle only if the network is not "idle" and, optionally, only if the network is not "near fully loaded," these terms being defined in relation to a token cycle. Therefore, no unnecessary purge marker frames are transmitted onto the network when it is idle or near fully loaded. Once purging is initiated, the purging station transmits at least one purge marker frame onto the ring network, and strips data received from the ring until a purge termination flag is set, upon detection of a received purge marker frame, a received token, or detection of a ring re-initialization procedure.

Abstract: Transceiver apparatus includes a transmitter circuit constructed with either emitter coupled logic (ECL) circuitry or programmable array logic circuitry, and a receiver circuit constructed with ECL circuitry. The transmitter circuit encodes a binary data signal received for transmission as a three-level modified duobinary encoded data signal and the receiver circuit decodes the received three-level encoded data signal to provide a binary data signal corresponding to the data signal received at the transmitter circuit for transmission. Both the transmitter and receiver circuits include features enabling transmitting and receiving high data-rate data signals.

Abstract: A linear servo circuit for A.C. motors is disclosed. The servo circuitry is used in a magnetic tape transport to control the motor which operates a tape reel on which the magnetic tape is stored. The servo circuitry develops two complimentary saw-tooth voltage waveforms synchronized to the sinusoidal A.C. line voltage. One saw-tooth waveform is used to control the motor in the forward direction and the other saw-tooth waveform is used to control the motor in the reverse direction. Comparator circuitry compares the saw-tooth waveforms to a D.C. control voltage which is proportional to the angular position of an arm that controls the tension of the magnetic tape. The comparator circuitry provides a control pulse to a photodiode when the saw-tooth waveform exceeds the D.C. control voltage. Light pulses from the photodiode impinge on a light sensitive SCR which in turn triggers a triac to apply power in the forward or reverse direction to the A.C. tape reel motor.

Abstract: Apparatus for effecting movement, translation and rotation, of an object relative to a reference, is disclosed, comprising transducer means having a portion thereof fixed with respect to the reference and means frictionally coupling the transducer to the object for effecting movement thereof. In addition, means for applying a predetermined potential difference waveform to the transducer to accelerate the transducer with respect to the object is disclosed. The transducer is accelerated at an acceleration which exceeds the critical acceleration of the object with respect to the transducer thereby effecting relative motion therebetween and thereby, being capable of moving the object significantly further than the extent of movement of the transducer.

Abstract: The servomotor outputs of two substantially identical servo channels, are connected through a differential mechanism to position an attitude control surface of an aircraft in response to common or separate, normally identical, command signals applied to the respective channels. Position and rate feedback means responsive to the movement of the control surface and each servomotor provides position and rate feedback signals to their respective channels. The primary position rate feedback term for each servomotor channel is derived from the position feedback means rather than from a servo tachometer to increase the stiffness of the output in resisting the motions commanded by a failed servo channel and to improve fault detection capability by increasing the difference velocity between a good and a failed channel.

Abstract: In an illustrative embodiment of the invention, an angular digital-to-resolver data converter apparatus is provided for converting a digital input signal representative of angular data into digital pseudo sine and cosine output signals representative of the angular data, which when converted into analog signals may be used to provide excitation to analog servo system resolvers. The digital or binary output signals which approximate the sine and cosine function of the digital angular data input signal are related such that the ratio of the digital output signal representative of the pseudo sine function to the digital output signal representative of the pseudo cosine function equals the true tangent of the actual angle.

Abstract: A geothermal energy recovery system of improved efficiency makes use of thermal energy stored in hot, solute-bearing well water as it is pumped upward to the earth's surface through an extended heat exchange element for continuously heating a downward flowing organic fluid to a supercritical state. Some of the energy of the latter fluid is used within the well for operating a turbine-driven pump for pumping the hot, solute-bearing well water at high pressure and always in liquid state to the earth's surface, where it is reinjected into the earth in another well. The temperature difference between the upward flowing brine and the downward flowing organic fluid is maintained finite in a predetermined manner along the subterranean extended heat exchange element.

Abstract: An illustrative embodiment of the invention provides a ship's steering system or helm adapted to provide a control signal to the ship's rudder such that the response of the rudder to the rotation of the helm is substantially non-linear from hardover to hardover wherein a portion centered about midship is linear such that hardover to hardover rudder can be ordered in less than one turn of the wheel. That is, less rotation of the wheel is necessary when large helm or rudder orders are required for heading changes and a greater rotation of the wheel about midships is necessary to desensitize rudder changes to large wheel rotations in order to make heading keeping easier.

Abstract: A force feel system for an aircraft having a control member or stick connected to a boost actuator for positioning an aircraft control surface and a variable force gradient spring mechanism for providing a feedback of artificial forces to the control stick, and which includes non-linear or irreversible linkage apparatus coupled between the stick and the variable force gradient spring such that the force feel system does not require the implementation of monitoring or redundant systems to provide fail safe operation in the event of failure of said force feel system. In addition, the "hands off" stability of the aircraft is not affected by the system because in this "hands off" mode of operation the non-linear linkage apparatus prevents the force actuator from moving the control stick out of the trim position.

Abstract: The servomotor outputs of two substantially identical servo channels, are connected through a differential mechanism to position an attitude control surface of an aircraft in response to common or separate command signals applied to the respective channels. The dual channels are continuously monitored in such a manner that if the velocities and accelerations of the two servomotor outputs do not track each other within predetermined ratio limits, appropriate servo brakes will clamp the output of the servomotor with the highest acceleration, or the failed channel. The rapidity with which the failed channel is detected and the servo brakes applied assures that essentially no control surface motion occurs and hence no attitude or flight path transients are evident by reason of the failure. Clamping of the failed servomotor, moreover, assures that the remaining servo channel may remain operative.

Abstract: The linear signal output range of a rotary transformer type device, such as a sine/cosine synchro, is considerably extended beyond its normal 45.degree. linear range by electronic circuit means. Specifically, the electronic circuit means utilizes the sine signal, which is generally linear from 0.degree. to 45.degree., as a portion of the output signal and utilizes a resultant signal computed from the cosine signal, which is linear from 45.degree. to approximately 135.degree. for the remaining portion of the output signal.

Abstract: A pre-burned ceramic cap cooperating with a notched metallic stud to anchor ceramic fiber insulating material in the interior wall of a furnace. The cap is provided with a slotted collar internally of the cap, so that on rotation of the cap surfaces on the collar engage surfaces on a notch to lock the assembly in position and to protect the metallic parts of the assembly from the deteriorating effects of combustion gas contact therewith.

Abstract: An illustrative embodiment of the invention relates to a preburned ceramic refractory covering for a water cooled member forming a structural portion of a metallurgical furnace. The covering comprises an inner layer of split ceramic refractory tiles at least partially encircling the structural member, and a C-shaped ceramic refractory collar which slideably engages the split tiles disposed about the member and supports the tiles thereon.