Abstract: An optical transmission system, especially useful in undersea applications, includes an optical path between two terminals with one or more repeaters located between the terminals for amplifying optical communications signals flowing in the optical path. The repeaters contain optical fiber amplifiers driven by pump lasers. The average optical power produced by the pump lasers is controlled in proportion to the magnitude of electrical line current produced by a controllable constant current source located in one of the terminals. This is achieved by regulator circuits which are responsive to a signal related to the magnitude of the line current and signals related to the actual optical output of the pump lasers. The magnitude of the line current may be conveniently set at the terminals so that the lowest bit error rate is achieved in the transmission system.

Abstract: A system and method for providing two-way video telephony between an originating location and a destination location, each equipped with an audio/video display (television) and an audio/video source (camera) using available channels dedicated for video telephony on one or more coaxial cable distribution networks which can be part of existing cable television systems. Each location is equipped with a network interface unit (NIU) which modulates outgoing audio/video information (which can be in analog or digital form) together with outgoing control messages onto an attached coaxial cable network. The NIU also demodulates incoming audio/video information and incoming control messages received from the attached coaxial network. Upstream signals may be transmitted to a cable network head end and then to the head end serving the destination location using demodulators, A/D converters (if not already in digital form), multiplexers, and the switched digital telecommunications network.

Abstract: Telephone headsets used by operators and airline pilot headsets are subject to substantial amounts of interfering ambient noise which detract from the intelligibility of incoming speech. Noise reduction circuitry does not altogether eliminate the interfering sound. A headset speaker and error microphone housing are disclosed which enable a greater amount of unwanted noise elimination. The speaker and microphone are configured closely with respect to each other and also to the user's ear. They are acoustically isolated in their own chamber. The microphone is located approximately on the speaker axis and protrudes substantially into the user's ear; and also is disposed close to the speaker cone surface. Additional acoustical tuning features include venting ports in the housing, and acoustic damping padding at the microphone entrance and on either side of the speaker. These expedients enhance the ability of the noise-cancelling circuitry to effectively reduce the undesired noise heard by the user.

Abstract: A system and method for establishing licensor changeable limits on shared software usage without the licensor having access to the system on which the shared software is running. An encrypted numerical limit value is embedded in the licensed software (program); when the program is executed ("accessed"), as a first step, the program decrypts the limit value and compares it to the number of users currently accessing the shared program. If the number of users is less than the limit, then access is allowed. If the number of users is equal to (or greater than) the limit, then access is denied.

Abstract: A status indicator for monitoring a fuse or a circuit breaker, including optically isolated triggering and alarm circuits which can be integrated into a fuse holder or circuit breaker housing. More particularly, a status indicator having an LED connected in series with a fuse or circuit breaker across a power source, and a phototransistor arrangement, connected across the power source, in series with an alarm circuit. The arrangement is configured so that as long as current flows through the fuse or circuit breaker, the LED produces light which causes the phototransistor to be maintained in a non-conducting state, and the status indicator to remain in a non-alarm state. Upon failure of the fuse or circuit breaker, current flow to the LED is interrupted, resulting in the phototransistor being biased into a conductive state, and the alarm circuit being activated.

Abstract: An optical receiver, e.g., receiver 10 (FIG. 1), has differential optical input beams and generates an electrical output. The voltage at an electrical node between series-connected optical detector diodes is clamped within a predefined voltage range by series-connected clamping diodes, to prevent the voltage from increasing when consecutive logic one optical input beams are received. Variable bandwidth and low energy dissipation are achieved since the resistors of high input impedance and transimpedance receivers are not required. A second optical receiver, e.g., receiver 20 (FIG. 2) is a monolithic, diode-clamped S-SEED with complementary optical input beams and complementary optical output beams.

Abstract: In order to mitigate against the multiplicative noise effects caused by known non-linearities in a trellis coded data transmission system, a signal constellation is formed by starting with a base constellation whose number of signal points and whose geometry are selected in accordance with conventional criteria and then warping that constellation by adjusting the positions of its signal points in accordance with a warp function which is the inverse of the known component of the non-linear characteristic of the transmission system. Because the constellation warping is deterministic, it is possible for the receiver to "unwarp" the received signal points prior to applying them to the Viterbi decoder. In preferred embodiments, the trellis code is of a type in which the dominant error event is a trellis path error.

Abstract: An amplifier with variable gain which maintains high Q when saturated. A resonant circuit is connected between collector outputs of a differential pair of transistors and RF chokes couple DC supply current to the transistors. The chokes have a high impedance at the desired frequency. The emitters of the differential pair of transistors couple together to form a common output which is connected to a current source. The amount of current from the current source substantially controls the gain of the amplifier. Because the resonant circuit is not shunted with a low impedance even when one of the transistors saturates, the Q of the resonant circuit is maintained.

Abstract: Device for electromagnetic emission depends on total internal reflection-on whispering gallery mode cavitation about the periphery of a disk-shaped element of sub-wavelength thickness. As a laser, operating above threshold, the design is alternative to that of the Surface Emitting Laser for integration in integrated circuitry-either all-optic or electro-optic. Operating below threshold, it may serve as a Light Emitting Diode. The same operational considerations-based on improved efficacy for whispering gallery mode devices as due to relevant dimension/s of sub-wavelength thickness-is of consequence for a category of devices serving other than as simple emitters. Such three port devices may serve as switches, modulators, etc.

Abstract: Use codes representative of uses of calls are defined as a part of a network numbering plan, and a route or a destination for a call is selected in full or in part on the basis of the use code dialed by a caller in conjunction with the called number via a call-processing arrangement (200) that uses stored definitions of syntax (320, 350) and grammar (400, 410) of the network numbering plan.

Abstract: In accordance with the invention the birefringence induced by compressive strain in silica waveguides on silicon substrates is compensated with a high index patch--such as silicon nitride--placed adjacent the core. The patch is disposed sufficiently close to the core to optically couple with the transmitted optical mode. The patch is preferably wider than the core to intersect the exponential tail of the transmitted optical mode. Such a high index patch preferentially couples TE polarization modes. By choosing an appropriate length for the patch, both strain and bend birefringence can be compensated.

Abstract: To recover the bits from various users in an asynchronous CDMA communications system, samples of the received signal are processed using blocks of code coefficients. Each code coefficient block includes the sequence of code coefficients for each user which formed the received signal samples. Each sequence has the same number of code coefficients and this number is equal to the product of a predetermined number of bit intervals and the number of code coefficients per bit interval. Processing of the received signal samples using this block formation completely eliminates interference including the so-called leading and lagging edge effects and can be implemented with blocks that include the code coefficients in one or more bit intervals.

Abstract: A test (i.e., a set of test vectors) for differentiating between two different integrated circuit versions (12,14) is established by first modeling the circuits in a simulated system such that: (a) the corresponding inputs of the circuits are coupled in parallel, (b) the corresponding outputs of the circuits are exclusively OR'd by a separate one of a plurality of exclusive OR gates (18.sub.1,18.sub.2,18.sub.3 . . . 18.sub.m), and (c) the outputs of the exclusive OR gates are OR'd by an OR gate (20). Thereafter, a set of test vectors is generated, using conventional techniques, such that the vectors, when input to the different-version integrated circuits, cause a predetermined logic level signal to the OR gate (20).

Abstract: Long delays in bidirectional multiplex section-switched self-healing ring transmission systems are avoided by eliminating looping of communications signals when restoring them in response to a failure in the ring and by distributing switching of paths to be protected to ring nodes other than those immediately adjacent the failure. This is realized by provisioning each node in the bidirectional multiplex section-switched ring transmission system with a map of its traffic pattern (all active tributaries) and the relative position of each ring node in the ring transmission system, and allowing the ring node, if it has communications traffic affected by the failure, to bridge and switch to and from the protection path.

Abstract: Novel superconductive oxides are disclosed. The oxides all have layered perovskite-like crystal structure and manifest superconductivity above about 77K. An exemplary material has composition Bi.sub.2.2 Sr.sub.2 Ca.sub.0.8 Cu.sub.2 O.sub.8. Other materials are described by the nominal formula X.sub.2+x M.sub.n-x Cu.sub.n-1 O.sub.2+2n+x/2.+-..delta., where X typically is Bi, or Bi together with Pb or other appropriate substituent, M is one or more divalent ion or mixture of monovalent and trivalent ion, n is an integer greater than 3, x=p/q, where p and q are integers and p<q, and .delta. is less than 0.5. Associated with the inventive compounds typically is a superlattice structure, with T.sub.c of the compound typically being correlated with the superlattice spacing. The inventive compounds are typically relatively ductile.

Abstract: A technique is provided for manually performing a soldering operation on an article with a low-solids flux-containing solder to bond an object to the article with a reduced amount of flux residues. The technique is practiced by first manually applying heat to the article and to the object which is in contact therewith, such as by contacting the article and/or object with a heated tip of a soldering pencil, iron or gun. Once the object and article have been heated, a low-solids flux-containing solder is then applied so as to be reflowed upon contact with the heated article and the object in order to bond them together when the solder solidifies. Simultaneously, heated air (i,e., air heated above the ambient temperature) is directed at the article and the object towards the region where the solder is being applied to maintain any flux vapors, which were created upon heating of the solder, in their vaporous state.

Abstract: A technique for the masking of quantizing noise in the coding of audio signals is adapted to include geometric interpolation between the thresholds for a tone masking noise and for noise masking a tone, in order to reduce use of bit-rate capability where it is not necessary for transparent or high quality. The technique is usable with the types of channel coding known as "noiseless" or Huffman coding and with variable radix packing. The stereophonic embodiment eliminates redundancies in the sum and difference signals, so that the stereo coding uses significantly less than twice the bit rate of the comparable monaural signal. The technique can be used both in transmission of signals and in recording for reproduction, particularly recording and reproduction of music. Compatibility with the ISDN transmission rates known as 1 B, 2 B and 3 B rates has been achieved.

Abstract: A hybrid wafer probe (10) for probing metallized areas (12) on a substrate (14), such as a semiconductor wafer, includes an insulative member (16) having a ground plane (21) on at least one of its major surfaces. Embedded within the insulative member (16) is a plurality of wires (24) each having a first end (26) protruding beyond the member for connection to a testing machine. Each wire has a second end (28) provided with a sharp tip (30) that protrudes through the member (16) in a region spaced from the ground plane (21) so as to depend below the member for making contact with the metallized areas on the substrate to be probed. By displacing the member (16) relative to the substrate (14) while the tips (30) of the wires 24 are in contact with the metallized area, the tips can scratch the surface of the metallized areas to make a reliable electrical connection therewith.

Abstract: A code-excited linear-predictive (CELP) coder for speech or audio transmission at compressed (e.g., 16 kb/s) data rates is adapted for low-delay (e.g., less than five ms. per vector) coding by performing spectral analysis of at least a portion of a previous frame of simulated decoded speech to determine a synthesis filter of a much higher order than conventionally used for decoding synthesis and then transmitting only the index for the vector which produces the lowest internal error signal. Modified perceptual weighting parameters and a novel use of postfiltering greatly improve tandeming of a number of encodings and decodings while retaining high quality reproduction.

Abstract: A phase-shifting lithographic mask is fabricated, in one embodiment, by using a resist layer that is negative tone with respect to a (patterned) electron beam and is positive tone with respect to a (flood) mid-ultraviolet beam, with the tone of the electron beam predominating over that of the mid-ultraviolet beam. The resist layer is spun on a body comprising a patterned metallic layer located on a (transparent) quartz slab. The body is subjected from below to a flood mid-ultraviolet beam and from above to a patterned electron beam whose edges are located somewhere in the midst of the patterned opaque layer but are not coincident with any edges of the patterned opaque layer. Thus, a subsequent development of the resist layer removes those regions and only those regions of the resist layer upon which the ultraviolet beam was incident--i.e., not in the shadows cast by the patterned opaque layer--in the absence of incidence of the patterned electron beam.