Abstract: A digital comparator for determining whether a digital test signal qualifies as an expected logic level, particularly suited to in-circuit digital testing applications. First and second comparing circuits, each formed by a differential amplifier circuit, receive the test signal, a high threshold signal and a low threshold signal. A control circuit selectively enables and inhibits the two comparing circuits so that only one is operative at any instant depending on the expected level of the test signal. The output terminals of the comparing circuits are connected so that the enabled one of the comparing circuits directly provides a pass/fail indication. A standby circuit allows both comparing circuits simultaneously to be selectively energized or deenergized, and an input buffer circuit permits the selective variation of the input impedance of the comparing circuit on the basis of the type of test being performed.

Abstract: During the in-circuit testing of electronic components, stimulus pulses are applied to a circuit bus producing an improper output signal, and the response of the circuit at various nodes connected to the bus is sensed with a current probe. An output signal from the current probe that is indicative of the magnitude and relative direction of the sensed current is sampled during each of the stimulus pulses to thereby isolate the portion of the output signal relating to the pulses from any noise in the circuit being tested. The sampled signal is further integrated to provide an additional measure of isolation, so that the probe signal processing circuit is relatively insensitive to both constant, high frequency noise and random, irregular or low frequency noise components.

Abstract: A data channel for a digital tester includes a random access local memory containing a main vector sequence, a subroutine vector sequence, and a test vector list. An index register is loaded with the address of the first vector in the list of vectors that is to be inserted as a variable into a vector stream. A sequence instruction selects the index register as the source of a test vector address when a variable vector is to be inserted into the vector stream at a point in a subroutine. The sequence instruction also resets the index register to a state which determines the address of the next variable to be inserted into the test vector pattern.

Abstract: A method and system for loading test data into individual pin memories of an automatic digital test system, particularly of the in-circuit type. Test data in the form of test vectors are accessed from a test vector store simultaneously with the access of a digital test pin selection signal. The test pin selection signal accessed with the test data is then used to selectively load the test data into a pin memory identified by the pin selection signal, thereby permitting the loading of test data into any one of a group of individual pin memories. In the preferrred embodiment the test data, a test vector, is stored in a test vector store in association with a test pin selection signal. When the test vector is read from memory, the test pin selection signal is also read by the same address signal.

Abstract: A lightweight marker adapted to be secured to an object for detecting the presence of that object within an applied magnetic field, the marker comprising a strip of ferromagnetic material having a magnetic and physical properties designed to generate a detectable signal whenever an object bearing the strip is placed with the field, cover means for protecting the strip and attaching it to the object, and a low friction release material between the cover means and the strip for affording relative slippage between the cover means and the strip, thus limiting the transfer of any mechanical stress applied on the marker to the strip.

Abstract: A handle for use with a computer disk pack memory unit which handle comprises a first and a second part assembled together to provide the releasable engagement of an axle within the computer disk pack and which two-part structure permits the fabrication of the entire handle by holding techniques.

Abstract: A variable magnification optical assembly having a housing with a fixed location for its object and image windows, and a carriage which is linearly moveable within the housing and which has mounted thereon at least one mirror. The carriage mirror(s) cooperates with at least one mirror affixed on the housing to define a first and a second light path within the optical assembly; with the respective paths being dependent upon the position of the carriage within the housing. The various mirrors are positioned within the optical assembly such that the light paths have different conjugate ratios. Therefore, a change in the magnification obtained within the assembly is accomplished with only a linear displacement of the carriage.

Abstract: A method of locating a splice within an endless loop of magnetic tape by detecting the presence of a magnetic marker attached to the magnetic recording tape wherein the magnetic marker is comprised of a magnetic layer having a flux density of at least 0.05 line of flux per centimeter of width, a thickness of not greater than 60 microns, and a coercivity of at least 1,000 oersteds, and which has a detectable magnetic pattern recorded thereon.

Abstract: A sheet feeder for feeding a single sheet from a stack of sheets by using a rotating cylindrical feed roller having a truncatel portion spaced away from the stack and a full diameter portion able to contact the stack whenever it is lifted by a lifting arm, which is pivoting in a timed relationship to the feed roller. This device simplifies sheet timing and eliminates the need for a constant biasing of the stack against a feeding member.

Abstract: A device for detecting and indicating a depletion of the supply of sheets in a sheet feeder of the type having a lifting arm used to lift the sheets toward a feeding member. The device utilizes the increased movement of the lifting arm due to the depleting stack to energize an indicator. The device also has the capability of utilizing magnetic members to latch the indicator in an energized condition until the supply of sheets is replenished, which then automatically de-energize the indicator.

Abstract: A window structure having a film supported optically flat between panes of glass, with the film secured at two opposing ends by a strip of metal grasping the film. The strip is held in a retainer resiliently secured in the glazing channel of the window. The glazing frame also includes side pieces and corner keys which support the opposed channels in spaced fixed relationship.