Abstract: A signal limiting amplifier includes interstage limiting devices to restrict the range of output voltage signals. The devices are base-emitter circuits of transistors, one of which operates in response to one polarity of signals and has its collector terminal unconnected, and the other of which operates in response to the other polarity of signals and has its collector circuit connected (when limiting) to operate an appropriate utilization circuit. In one embodiment, the limiting amplifier is applied as a common mode feedback amplifier in a telephone line feed circuit, and the limiter signal is used to limit large longitudinal signals on a customer line and to power down the line feed circuit in the event the limited signals persist beyond a certain interval.

Abstract: A plural band telescopic antenna, including a band for frequencies much higher than the frequencies of the AM/FM band, is realized by making one telescopic section into a dipole high frequency antenna with its coaxial cable feed line extending through the telescopic antenna to the feed point of the one section. A double-tuned dipole embodiment and different arrangements for coupling the feed line through a rotational drive force applying mechanism are shown. In one embodiment, the line feed is also used for coupling mechanical extension and retraction forces to the one section.

Abstract: A single chip, bipolar logic circuit receives input signals in a differential amplifier or comparator stage coupled, without saturation, by differential current mirrors to drive an output stage of the push-pull variety. Various circuit arrangement are included to keep other bipolar transistors out of their saturation operating regions, and master transistors of the current mirror are provided with trickle bias when in the operating state to hold them at turn-on threshold for fast response to changes in state of the digital signals.

Abstract: A plural band telescopic antenna, including an added band much higher than the frequencies of the AM/FM band, is realized by making one telescopic section into a center-fed, high frequency antenna and using its coaxial cable feed line for also coupling mechanical extension and retraction forces to that section.

Abstract: A twisted ring counter has a NOR gate with inputs from outputs of the last two stages thereof to detect and be activated by a combination of outputs which is found in all modes of operation of the counter. When activated by the combination, the gate provides an output to reset the counter to an all-ZEROs condition.

Abstract: A laser-driven interferometric signal sensing system has a cleaved-coupled cavity laser with separate stabilization servo loops of different time constants for the modulator and laser sections thereof. The laser section is biased above lasing threshold, and its stabilization loop is operated at a frequency twice the frequency of laser section bias current modulation. A laser loop feedback error signal is a function of predetermined, environmental-type, parameter variations in the sensing location and is processed to be a function of the second derivative of interferometer output intensity with respect to laser section current. That error signal is applied to modify laser section bias current in a direction to zero out the feedback signal.

Abstract: A multishelf main distributing frame for lightguide fibers is provided in which each shelf includes a pair of spaced plates (67,68) for receiving cable fibers from the rear portion of the shelf, receiving cross-connect jumper fibers from the front portion thereof, and having one or more removable connector panels (30) for terminating lightguide fibers at opposite sides thereof. The panels are recessed from the front edges of the shelf to assure room for a predetermined minimum bending radius for jumper fibers connected to the front of the panels. Once such panels are installed, they cooperate with the shelf plate members and with a windowed cable channel (17) at the rear of the shelf for protecting relatively lightly sheathed individual fibers of cables passed through the channel into the shelf region. A hinged closure (24) is provided at the front of each shelf for protecting cross-connect jumper fibers of that shelf without subjecting those fibers to possible mechanical damage when the closure is closed.

Abstract: An origination scan circuit for detecting circuit closure state in a loop circuit has a much lower impedance than does the typical loop circuit. Its source impedance is split into separate resistive parts for connecting opposite terminals of an office battery to the tip and ring leads of the loop. Currents in the separate resistive parts are sensed and summed for comparison against a threshold current to indicate whether or not a subscriber station on the loop is off hook. Threshold current magnitude is variable to accommodate loop start and ground start applications. When the off-hook state is detected, the origination scan circuit is disabled by switching open the resistive part connections, and loop current is thereafter provided by other suitable means. Automatic current limiting arrangements are included for converting the switching functions to high impedance circuit elements.

Abstract: An interface circuit includes programmable registers both for making provisioning signals available to a set of electric circuit devices, and for monitoring operation of at least a portion of those devices. Signals received from a control source are employed to program the registers and to provision device control memories enabled for that purpose by one or more of the registers.

Abstract: An arrangement is shown for combining multisource randomly occurring data, such as seismic or sonar data, into a single output signal. Histories of simultaneously occurring data from each source are accumulated, and their power levels compared to determine which is likely to have significant data, as distinguished from noise. The largest of the data so compared in a given time epoch determines the source to be used in a succeeding epoch to provide the output contribution for that succeeding epoch.

Abstract: Resistive circuits are provided at the input of an electronic battery feed circuit feedback path for lowering the voltage level of feedback signals to a metallic signal feedback portion and a common mode signal feedback portion so a common mode amplifier can be implemented in a much lower voltage technology than line amplifiers of the battery feed circuit. Additional resistive circuits at the feedback output apply metallic signals to complementary inputs of the tip and ring line amplifiers without requiring a phase splitting amplifier. In addition, signals derived from the feedback circuit are used to vary the supply voltage for the line feed circuit elements as a function of feedback signal level and to provide a common mode reference signal which causes the tip and ring amplifiers to be biased symmetrically with respect to ground and the variable negative supply.

Abstract: Received data signals in digital form are sampled a plurality of times during each bit interval and weighted to enhance the statistical effect of a predetermined intermediate amplitude range prior to accumulation over a bit time to obtain an initial average indication of bit value. Plural repetitions of the same bit received at different times are similarly processed and the averages weighted according to received signal strength at the time of reception. Then the weighted averages are accumulated in a two's complement arithmetic fashion so that the accumulation sign bit binary signal state indicates the binary value of the bit. In one embodiment, the initially derived multiple samples of each bit are converted to in-phase and quadrature-phase versions prior to the sample accumulation step; and the separate accumulations of each version are utilized to obtain an arctangent value for adjusting the phase of a local clock to that of the received data.

Abstract: An operational amplifier is provided with at least one output supplementary stage and current mirror amplifiers for coupling amplified signal current variations to drive supplementary output stage source and sink transistors. Those transistors have their internal collector-emitter paths directly connected between supply rails and perform further amplification of the signals. A current source circuit is employed for so limiting those signal current variations that, after the further amplification, circuit devices will not be damaged.

Abstract: A determination is made as to whether or not each word of a segment of a body of text is included in one or more multi-word subjects of a list of subjects included in the text. If a subject word is found, a further determination is made as to whether or not all words of the subject are included in the same segment. A subject, as to which all words are in the same segment, is associated with text-locating indications for indexing purposes. Routines are also shown for updating a window portion of a textual manuscript for indexing purposes, searching a word list for matches and forming an active list for words which match, performing approximate root matches, and determining from an activated word match which subjects of a subject list are found in their entirety in a manuscript text.

Abstract: A distortion simulating pilot is injected at the input of an amplifier which uses feed forward distortion correction. The magnitude of the pilot signal in the amplifier output is used to control a decreasing step size circuit algorithm for adjusting the gain and phase of the feed forward distortion signal to eliminate substantially the pilot signal and the distortion introduced by the amplifier.

Abstract: In a buck-boost, switching regulator, separate signals are developed to control duty cycles of regulator switches. Control exercised by a pair of feedback-determined reference signal voltages through which a ramp signal is swept at inputs of separate comparators, comparator outputs control respective switches. A predetermined maximum voltage difference is permitted between the reference signal voltages. The reference used to control switching of one end of the regulator inductance is limited to a minimum voltage corresponding to a minimum duty cycle greater than 0% while the other reference is used to control the other end of that inductance and is limited to a maximum voltage corresponding to a minimum duty cycle less than 100%. A current limiting feedback from one of the switches is operated in response to current in excess of a predetermined level to force the ramp signal to a level corresponding to 0% duty cycle for both switches at the same time.

Abstract: A switchable common mode reference circuit for tip conductor and ring conductor line feed amplifiers provides a tip-ring common mode feedback reference for loop-start operations and a common mode fixed bias for ground-start operations. The functioning of the line feed arrangement is enhanced by using separately-sensed tip and ring current signals to control the switching function and by switching the line feed amplifiers between a current source mode for loop-start operation and a voltage source mode for ground-start operation.

Abstract: A data signal is processed to change its form and spectral content without introducing undesirable frequency and amplitude effects. Multiple data signal states, which determine the essential characteristics of the output signal wave configuration, are utilized in conjunction with clock signals at a rate substantially in excess of twice the largest frequency component of the data signal in order to read from a memory a bit-duration waveform sample set representing the desired output signal wave configuration. Predistortion to compensate for anticipated transmission effects is also included in that configuration. In one embodiment, an input data signal is in an NRZ format and is processed for conversion to the biphase, or Manchester, format by a ROM table look-up function addressed jointly by the input signal states and the clock signals.

Abstract: Database locations for user-supplied query keywords are individually determined. Those locations for the full set of query keywords and for successively smaller groups of such query keywords are screened for locations common to all words of a group. The screening is stopped after all query keywords have been considered and found to have been included in at least one of the tested groups of query keywords having a common database location.

Abstract: A topic announcement routine is provided and is called by an announce flag included in a flag field of an author-selected topic title definition in a course material database. Each call of such a flagged topic causes the routine to display for a student an announcement that a new topic is about to begin, and to make available to the student an opportunity to select a command from a predetermined set of commands including at least one address-generic transfer command. Control flags, such as an announce flag or the presence of text in the title field of a topic definition, are employed for various purposes, such as marking the end of transfer under a transfer command for that topic, or disabling selected commands of the set.