Abstract: Conventional telephone systems including terminal equipments interconnected by a communications channel typically employ a supervisory tone transmitted by each terminal equipment to indicate its idle condition. Because the fraction of idle terminal equipments may be high, the total energy carried over the channel is substantially determined by these tones. The apparatus of the type disclosed herein, employed in association with each terminal equipment, effects a reduction in the channel power loading due to those tones. The apparatus includes circuits for detecting the presence of the idle state supervisory tone being transmitted from or received by the associated terminal. If the tone is present on either the transmit or received lead, the signal transmitted by the terminal into the channel is attenuated by a fixed power ratio and the signal received by the terminal from the channel is amplified by the same fixed power ratio.

Abstract: An optical record and playback system is described for use in a multi-channel data processing system. An optical head which includes a laser diode array comprises a collection objective, an anamorphic beam expander and a focusing lens. The optical head collects the laser beams emitted by the diode array, expands the beam cross-section to form circular beams and focuses the beams to diffraction limited spots.

Abstract: An optical record and playback system is described for use in a multi-channel data processing system. An optical head which includes a laser diode array comprises a collection objective, an anamorphic beam expander, a relay lens and a focusing lens having a finite conjugate. The optical head collects the laser beams emitted by the diode array, expands the beam cross-section to form circular beams and focuses the beams to diffraction limited spots. In operation the relay lens is used to image the lasing spots from the laser diode array in the conjugate plane of the finite conjugate focusing lens.

Abstract: A transceiver provides data collision detection and avoidance in a contention-formatted, FDM communications network using FSK modulation. Locally-generated baseband data is compared to recovered baseband data received from the system bus. A failure to compare indicates that there has been a data collision. The wide disparities in amplitude between locally-generated FDM signals and signals received from the bus are accommodated by a signal splitter which provides greater attenuation of the local signal than the generally weaker bus signal, and by the use of logarithmic amplifiers which generate relatively constant output levels for a wide range of input signal amplitudes. Collision avoidance is provided by monitoring the bus signal demodulators for data activity, and by inhibiting the local transmitter when such activity is detected, subject to an override during transmission by the local station.

Abstract: In an optical scanning system suitable for use in an aircraft for ground contour measurements, wherein the received image from an illuminated ground spot is reflected from a rotating prism onto paraboloidal mirrors which focus the image at a common focal point, and wherein the rotating prism is also used to transmit the scanning spot-illuminating beam, a wedge-shaped light guide accepts the coincident focused images and funnels them into a photoelectric detector. Because the prism rotates at high speed, variations in light signal transit times due to differences in target distance over the range of the scan cycle and due to differences in aircraft altitude cause the image focal point to shift, necessitating a relatively wide rectangular input aperture on the light guide, resulting in the admittance of large amounts of background light in to the detector.

Abstract: A frequency synthesizer for controlling the frequency f.sub.0 of a signal e.sub.0 in response to a control signal e.sub.c2 to produce a band of selectable frequencies separated by .DELTA.f between the frequencies f.sub.x and f.sub.y, where (f.sub.x +R.DELTA.f)=f.sub.0 and R is zero or any integer .ltoreq.(f.sub.y -f.sub.x)/.DELTA.f. The invention includes a first generator for generating the signal e.sub.0, a second generator for generating a signal e.sub.1 having a band of selectable frequencies separated by .delta.f, where .delta.f>>.DELTA.f, a frequency subtractor for subtracting f.sub.1 from f.sub.0 to produce a signal e.sub.2 of frequency f.sub.2. Also provided is a third generator for generating a variable preliminary reference signal of frequency f.sub.pr consisting of a band of selectable frequencies separated by M.DELTA.f and lying within the frequency band Mf.sub.x to Mf.sub.y, where (Mf.sub.x +R.multidot.M.DELTA.f)=Mf.sub.r2 ; a divider for dividing Mf.sub.

Abstract: The focus actuator, turntable and translation stage in an optical disc record/playback system may effect relatively large reaction forces on the components of the system. These reaction forces can cause vibrations which interfere with or distort information recording or retrieving operations which occur at the same time that high speed access is being effected. A momentum compensating mass is coupled to the focus actuator, turntable and other moving elements to reduce or eliminate the reaction forces which can affect system operation.

Abstract: In optical disc systems a record level control is provided for adjusting the power of the recording source. The waveform of the data detected during a read-after-write operation contains information concerning the power of the record source. These read-after-write signals are the same as those that are used during an actual playback operation. The record level control is implemented in two ways. In the first, the detected data is averaged to determine the record level. In the second technique the detected data is compared with an "ideal" signal derived from the detected data to provide an indication of a high or low record level. Further, the system includes means for adjusting the record level in response to an indication of a variation in the record level.

Abstract: A high speed data storage and retrieval system for use with disc record media includes a storage module for holding a plurality of discs, a read/write station and a changer apparatus for transporting discs between the storage module and the read/write station. In a preferred embodiment the storage discs are enclosed in a protective cartridge and held in place in the cartridge so that the recording surfaces of the disc do not touch the inside surfaces of the protective cartridge. The changer apparatus includes a pair of belt elevators. One of the elevators designated the "up" elevator transports a selected disc from the storage module to the read/write station. After processing, the selected disc is returned to the storage module via a second elevator which is designated the "down" elevator. A pivot block assembly is used to aid in the transfer of disc from the "up" elevator to the read/write station and from the read/write station to the "down" elevator.

Abstract: A record package includes a disc record housed within an enclosure. The enclosure comprises thin membrane covers held in tension between a metallic outer frame and two inner rings. The inner rings include dust seals which are held against the disc record by the tension of the membranes. When the disc record rotates, the windage it creates lifts the dust seals from the disc record. The use of a clear membrane eliminates the need for a sight window when recording on the playing back from an optical disc record.

Abstract: In a communications receiver where the AGC signal derived from a phaselock detector is used to measure input signal strength, and that measurement is subject to error as a result of the nonlinear devices used in the carrier demodulation, a signal having inversely corresponding error characteristics is summed to the phaselock detector AGC signal to produce an improved AGC signal which is substantially linearly related to the input signal. That signal, having the inversely corresponding error characteristics, has been found to be the signal representation of the envelope of either the positive or negative cycles of the input signal.

Abstract: A protective cartridge is provided for a disc record in a disc playback/record system. The protective cartridge is provided with a compliant annular section and a central portion. A first annular magnet for use in holding the disc record against a turntable, while the turntable rotates, is positioned in the central portion. A ram which includes a second annular magnet is arranged such that its polarity is opposite to the first magnet. When the ram is lowered an engagement of the disc record is effected. That is, the second magnet repels the first magnet to cause the first magnet to hold the disc record against the turntable.

Abstract: A rapidly-spinning motor-driven disc is quickly brought to a halt by utilizing the motor in a controlled current dynamic feedback mode. An electrical signal is provided to cut off the motor braking current when the rotating motor shaft reaches substantially zero velocity, thereby avoiding any residual rotation of the disc. As the disc slows at a constant deceleration rate, the apparatus measures the relative time durations of two consecutive pulses which represent equal displacement arcs on the disc. From these data the time at which zero velocity will be achieved is computed, and the motor current cutoff signal is generated at the proper instant.

Abstract: A wideband optical disc data record/playback apparatus is provided. The apparatus includes means for splitting the output of a single laser into multiple beams. The record beams are independently modulated and used to simultaneously record data at extremely high rates on the surface of an optical disc. The apparatus is capable of recording 1.times.10.sup.11 bits of data on one surface of an optical disc at data rates of 100 to 300 Mb/s. In addition, a plurality of coplanar low power beams are used for playback and data verification purposes. In the playback mode a single beam is split into a plurality of low power beams and one of the plurality of beams is dithered such that the dithered beam exhibits periodic excursions in a radial direction across the surface of the disc. The dithered beam is used for tracking purposes in both the playback and record mode. In a preferred embodiment the playback beams are split by an optical grating and dithered by an acousto-optic device.

Abstract: Heating elements and temperature sensing devices are positioned in diametrically opposed pairs along a tubular boom extending outwardly from a spacecraft. As temperature differentials are detected across the diameter of the boom, current is selectively applied to the heating element on the cooler side of the boom to equalize the temperature and prevent boom distortion. In another application, current may be selectively applied to a heating element to cause bending of the boom to achieve a desired positioning of the tip portion of the boom.

Abstract: A reflection phase shifter includes transmission-type fractional phase shifters and a reflection-type fractional phase shifter. The fractional phase shifters include PIN diodes and transforming sections for transmission line matching. Three fractional phase shifters provide 45-, 90-, and 180-degree delays. The individual fractional phase shifters are selectably "switched in" by the application of bias signals.

Abstract: An extendible tubular boom includes a metallic ribbon which is prestressed to assume a rigid tubular shape when extended and which can be flattened and coiled for storage, and a plurality of conductive foil strips fixed to the ribbon which provides electrical paths between sensors located at the tip of the boom remote from the spacecraft and electronics located within the spacecraft. Remote positioning of sensors permits the measurement of parameters of the local plasma without the perturbing effect of the presence of the main body of the spacecraft. The conductive foil strips are electrically isolated from the metallic ribbon comprising the boom structure by a layer of insulating material. Both the foil strips and the insulating layer are sufficiently flexible so as to withstand the transverse and longitudinal stresses encountered as the boom is furled and unfurled.