Abstract: A solid state protector unit has a single voltage protection device shared by both tip and ring conductors to protect telephone equipment in a central office or other location from surges of voltages in either tip, ring, or both tip and ring conductors. The voltage device has a surge-suppressor sandwiched between two metal plates. Each of these pairs of metal spring clips retain a pair of diodes in contact with and on opposite sides of the two metal plates. When a voltage surge exceeds a predetermined threshold, the surge-suppressor turns on and permits a current to flow through it to a ground, thereby protecting the telephone equipment from voltage surges. Heat generated for a sustained period from the voltage device or from the current device will cause the current device to be grounded permanently.

Abstract: A second order gradient microphone with unidirectional sensitivity pattern is obtained by housing each of two commerically available first order gradient microphones centrally within a baffle. The baffles have flat surfaces, are preferably square or circular and have parallel surfaces the two baffles being parallel to each other. The rotational axes of the microphones are arranged to coincide. The output signal from one of the microphones is subtracted from the delayed signal output of the other.

Abstract: Pulses from a first laser source (10) at a predetermined high repetition rate are passed through an isolator (38), a mode-matched with an amplifier and then temporally multiplexed to a predetermined high repetition rate. The high repetition rate pulses (63) are then injected into a second source (70) where they are amplified to derive a stream (79) of high power pulses at the predetermined high repetition rate and then selectively released.

Abstract: A compliant, synthetic material of predetermined thickness is inserted into the space between cables and the inner surface of a pedestal enclosure which houses the cables. The compliant material prevents moisture, rodents, and insects from entering the upper portion of the enclosure. Drainage slots are provided. A wire mesh pad or steel wool may be used instead of the compliant, synthetic material. A plurality of embodiments are disclosed.

Abstract: A digital synthesis technique provides pulse shaping in accordance with predetermined time domain and frequency domain constraints. In the technique, the informational content of a binary bit stream is used by an access circuit (12) to form address words for accessing a read-only-memory (13). The digital representations stored in the ROM (13) represent a superposition of temporally-displaced truncated impulse time functions, each weighted by the discrete transmission symbol levels of the analog output signal. The digital representations from two ROMs (13-1 and 13-2) are toggled by a sequencng circuit. In other embodiments of the invention, different memory arrangements ranging from a signal ROM (142) to an array of ROMS (163-1 through 163-3 and 164-1 through 164-3) are respectively used to decrease circuit complexity. In a digital radio transmission application of the technique, this arrangement is economical, readily reproducible and stable since it obviates the need for conventional complex analog filters.

Abstract: Supervisory audio tones received from a mobile telephone unit are converted from analog to digital form. The tone is then converted to a complex number by bifurcating the tone path and multiplying one path by a sine function and the other path by a cosine function. The complex numbers are accumulated and the frequencies where significant power exists is found using the discrete Fourier transform. If the power at an assigned frequency exceeds a threshold, the corresponding supervisory audio tone is declared to have been detected.

Abstract: Undesired signals from interfering satellites are separated from desired signals from a target satellite by using a sum beam and a difference beam as in a monopulse radar. Both desired and undesired signals are received by an antenna and separated by different mode couplers from a waveguide. The fundamental mode of the waveguide provides the desired signals along with components from the interfering signals. Both desired and undesired signals are picked up from the waveguide through a fundamental mode coupler. The higher order modes of the waveguide provide the interfering signals alone, representing the difference beam which will be aligned along the boresight. In a circular waveguide, the TM.sub.01.sup.o will yield a difference pattern for vertical polarization in any plane, and a TE.sub.21.sup.o or TE.sub.01.sup.o mode will result in a difference pattern for horizontal polarization. A square or a rectangular waveguide could be used instead of a circular waveguide to achieve the same result.

Abstract: The power output from a laser transmitter is maintained within predetermined levels. These levels are maintained at fixed percentages on either side of the average laser output power which is transmitted, regardless of variations in ambient temperature. This is achieved by coupling the bias current control loop to the modulation current control circuit.

Abstract: A second order gradient microphone arrangement is implemented with four commercially available, inexpensive first order gradient electret microphones which are arranged in the wall of a hollow cylinder at ninety degrees angular spacings and whose outputs are added to produce a toroidal directional characteristic. The distance between the tops of the microphones and the top of the cylinder equals the distance between the bottoms of the microphones and the bottom of the cylinder. The directional characteristic is relatively frequency independent. The arrangement is characterized by rotational symmetry around the cylinder axis and further by a cosine squared dependence in the planes containing the rotational axis. In the direction of the axis, the sensitivity at midfrequencies is typically twenty decibels lower than in the equatorial plane. The equalized frequency response in this plane is within .+-.3 dB from 0.3 to 3 kHz.

Abstract: A printed circuit board has two contact areas on each surface near one end. The board is sandwiched between two halves of a shell to form a plug in such a way that the contact areas are exposed. The contact areas on one surface are nearer the exposed end than the contact areas on the other. The tip and ring conductors of a pair of wires in a test cord are connected, respectively, with the two contact areas which are nearer the exposed end. A keeper spring which is connected to the shield of the jumper cable, the ground potential, insures that the plug will be retained within a jack into which the plug is inserted by engaging a detent. The detent is connected to ground potential. The jack has two long electrical contacts and two short electrical contacts. The long electrical contacts engage the two contact areas which are farther away from the exposed end and the two short electrical contacts engage the nearer contact areas.

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: Data-aided equalization and cancellation in digital data transmission over dually polarized fading radio channels is disclosed. The present invention uses decision feedback structures with finite-tap transversal filters. Subject to the assumption that some past and/or future data symbols are correctly detected, formulas and algorithms for evaluating the least mean-square error for different structures are disclosed. In a sequence of curves, the performance of various structures for a particular propagation model and several fading events are evaluated and compared.

Abstract: In response to spurious signals in a circuit connecting telecommunications equipment with a serving central office, the signals will pass through terminals of a protector module and through a protector unit inserted in the circuit causing a lead pellet to melt or the air gap between carbon blocks to short and establish a path to ground so that the spurious signals may be grounded. When the protector unit is removed from the protector module, the circuit remains grounded until the protector unit is replaced. Alternatively, when the protector unit is removed, the electrical path of the circuit is opened by introducing an insulator in the path of signals between the terminals. In one embodiment, in the open circuit condition, unusually high voltages arc over from the protector terminals to a metallic pin and then to ground.

Abstract: In a telephone local exchange system where loops are connected to a remote switch which in turn homes on a host switch via a carrier system and where the distance between the ends of the loops and the host switch exceeds a threshold, the loops may be tested by locating the test apparatus remotely from the host switch so that the distance between the free ends of the loops and the test apparatus is below the threshold and so that a metallic pair of conductors may be used therebetween to permit some tests which cannot be done using carrier facilities. In order to establish a connection between the test apparatus and the loops, signals are transferred over two dedicated carrier channels between the test apparatus and the host switch via two applique circuits. These applique circuits make it appear to the test system as if the remote switch (or carrier RT or concentrator) support a test trunk.

Abstract: A wireless PBX or LAN system is disclosed that allows multiple, simultaneous users per channel for communication between a base station and a plurality of remote terminals by a combination of adaptive signal processing arrays using optimum combining at the base station for interference suppression and separation of desired signals, adaptive power control at the remote terminals to keep interference at acceptable levels, and adaptive retransmission with time division in the direction from the base station to the remote terminals for communication therebetween including sending power control information to the remote terminals. The adaptive signal processing arrays have a plurality of antennas at the base station, permitting a plurality of users in any one channel. If after adaptation a user's signal cannot be received adequately, the user is dynamically reassigned to a different channel. Interference is minimized by keeping the signals transmitted from and received at the base station at the same power level.

Abstract: A control signalling arrangement for a pulse transmission system uses a main data stream including a block parity channel. Control signals are transmitted from an end terminal to a repeater by inserting the control signals in periodically spaced bit positions of the block parity channel. At the repeater, the control signals are separated from the block parity channel for controlling the circuits or devices for maintenance operations.

Abstract: A connecting block for a digital cross connect system has printed wiring circuit boards to interconnect terminals on the rear surface with jacks and terminals on the front surface. The terminals on the front surface are multipled to jack appearances also on the front surface of the connecting block. The connecting block has a pedestal which sits on a lower crossarm of a frame. The upper surface of the connecting block has a resilient tang which snaps into an upper crossarm of the frame. The tang is depressed with a screw driver or the like to disengage it from the upper crossarm. The connecting block is suspended by the anterior section of the pedestal from a panel located in front of the lower crossarm to expose the terminals on the rear surface. Conductors in cables to and from digital systems are then terminated on the rear terminals.

Abstract: A single substrate with a stripline circuit on one of its surfaces for use in a down converting mixer has a thin metallic film deposited utilizing photolithographic techniques onto two free ends: one end with the junction section of the stripline circuit for establishing a ground path with the metal block upon which the substrate rests and the other end with the filter section of the stripline circuit for establishing the intermediate frequency signal path with the inner conductor of a coaxial cable.

Abstract: A female tee pipe fitting has a stop only in one of its three openings, the other two coaxial openings which are perpendicular to the first opening have smooth inner surfaces and no stops. When two pipes are to be connected, one of the pipes is severed and a section of pipe removed leaving two free ends. A smooth opening of the female tee pipe fitting is slipped over one free end of the severed pipe and then slid out to slide over the other free end of the severed pipe. After the female tee has been centered, the second pipe is inserted within the opening of the female tee pipe fitting with the stop and the joints sealed.