Abstract: A probe system for probing a device under test (DUT) includes a DUT support chuck for holding the DUT. A plurality of flexible probe needles are positioned along a "Z" axis that extends orthogonally from the surface of the DUT. Each probe needle is movable with respect to the DUT support chuck. A motor provides for relative movement, at least along the Z axis, between the probe needles and the DUT support chuck. A variable focus imaging system is positioned along the Z axis and provides image signals to a control processor. The control processor causes the variable focus imaging system to image the surface of the DUT and at least one probe needle. The control processor is responsive to a determined distance between focal planes containing the DUT surface and probe needle to cause the motor to move the probe needle and the DUT surface into physical engagement.

Abstract: Apparatus and method for collision avoidance in a multinode data communications bus, the bus having a plurality of nodes coupled thereto for transmitting and receiving data over the bus, the bus further including a BUS BUSY signal line bidirectionally connected in common between the nodes, each of the nodes being operable for asserting the BUS BUSY signal line and also for determining the state of the BUS BUSY signal line.

Abstract: An apparatus for monitoring a plasma torch includes a dedicated photometer which produces a signal representative of the temperature of a quartz tube of the torch, which signal can be used to reduce the temperature thereof.

Abstract: An atomic absorption spectrophotometer having a source, e.g., a hollow cathode lamp, of spectral radiation of a selected narrow band of wavelengths optically directed along an axis through an electrothermic sample atomizer and a field stop to a photoelectric detector. The sample atomizer is subjected to a substantially unipolar AC electromagnetic field having flux lines directed transversely to said axis to effect Zeeman splitting of the radiation into two orthogonally polarized components .pi. and .sigma.. Disposed in the optical path between the atomizer and detector is a stationary beam-splitting polarizer prism oriented so as to transmit the .sigma. polarized component and block the .pi. component. Mirrors are used exclusively in the optical systems so as to minimize the effect of dispersion and stray light.An electromagnet, used to generate the electromagnetic field, is connected to the AC power line in series with the diode and has a small capacitor connected across its coils.

Abstract: A method and apparatus is provided for compensating for repeatable error signal components which occur with information components. The method provides for detecting the peak amplitude of an error signal and providing a representation thereof, storing the representation, providing a composite electrical signal having the information and error components, detecting the peak amplitude of the composite signal and providing a representation thereof, and combining the stored error signal representation with the composite signal representation to provide an output signal from which the error signal component has been substantially removed.