Abstract: Modems, data service units, application modules and other data communication devices, installed in a common equipment cabinet, are interconnected by way of a time division multiplexed bus. Time slots assigned to the various devices recur at a number of regularly-spaced access periods across each time division multiplex frame. The rate at which the access periods occur and the total number of access periods that make up each frame are chosen in such a way as to accommodate a mix of devices having respective bus access rates wherein there is at least one pair of rates for which neither rate of the pair is a whole number multiple of the other. The process of allocating access periods to the time slots is carried out using a known lemma to identify linear Diophantine equation solutions.

Abstract: There is disclosed a message formatting arrangement which allows messages from a central processor to be distributed over a bus to a plurality of remote processors using a single address presentation for any message without regard to the byte length of the message. Each message consists of a variable number of sub-messages each having a 3-bit qualifier which specifies the sub-message type. Each remote processor is capable of determining the length of each sub-message depending jointly upon the value of the qualifier and upon the context byte which precedes each group of sub-messages. The remote processors having the capability of skipping over a variable number of idle frames without beginning to process a new message.

Abstract: A multiprocessor system automatically responding to a request for executing a new program to establish an extended process that spans a plurality of processors each having resources required for the execution of the new program. Initially, the extended process comprises an user process that is requesting the execution of the new program. Stub processes are created as required to gain access to the object code file of the new program, to allocate a processor to execute the new program, and to initialize the allocated processor for execution for the new program.

Abstract: Apparatus for discharging static electricity from the human body by ionizing air and utilizing the flow of ions from the apparatus into the surrounding environment to discharge the body. The apparatus utilizes two power supplies to raise two embedded electrodes positioned in a horizontal plane different voltage potentials with respect to the body. The air is ionized by utilizing discharge electrodes of the opposite polarity positioned over each of the embedded electrodes which results in air ions being formed in a ion distribution above each embedded electrode. The embedded electrodes are positioned a predetermined distance from each other in the embedded plane. Within the region between the embedded electrodes, the ions recombine to form air molecules. The ions in the distribution layers above each embedded electrode drift toward this region under attraction from each other.

Abstract: A frequency-hopping radio communication system is disclosed comprising a control unit which transmits to and receives from each of a plurality of slave stations using a frequency-hopping mode of operation. During a start-up mode, the control unit communicates a starting message to each slave station using a predefined frequency. The message identifies to each slave station a frequency-hopping sequence to be used to select the frequencies from a group of frequencies for transmission to and reception from the control unit. This message also specifies to each slave station unique starting frequencies in the frequency-hopping sequence at which to begin transmitting and receiving. All slave station transmissions are synchronized to the control unit transmissions, thereby preventing any two stations from concurrently using the same frequencies for either transmitting to or receiving from the control unit.

Abstract: A voice-band data symbol is typically impaired by so-called phase jitter prior to symbol being received at a data modem. Modem circuitry estimates the phase angle of the jitter and an infinite-impulse-response (IIR) filter adjusts to that phase angle so that the jitter can be corrected for by a demodulator circuit. Advantageously, the IIR filter is arranged so that its pair of complex, conjugate poles are initially positioned at a first predetermined radius within a unit circle. The angular displacement of the poles around the unit circle is adaptively increased in response to receipt of a series of such estimates until such displacement substantially equals the phase angle of the jitter. The poles are then positioned at a second predetermined radius to increase the gain of the filter.

Abstract: A device separates attached multiple printed circuit boards without damaging solder connections and delicate surface mounted components attached to the boards. The device comprises a pair of disc cutters positioned in opposed alignment and minimally spaced apart for providing a bifurcated cutting edge through which commonly attached sections of the printed circuit boards are conveyed while supported by a transporter. The contact pressure on the boards is limited to the commonly attached sections as they are engaged and conveyed by the cutting edge. Minimal stress and vibrations are imparted to the boards and therefore the components connected thereon with this device. The boards are thus separated while avoiding damage to the solder connections or the surface mounted components.

Abstract: The invention is directed to a telephone structure that eliminates the need for fasteners to assemble a keypad and secure the keypad in place in the telephone. This is accomplished by a telephone that comprises a hollow housing (100) having a face portion (120) that includes an array of holes (122) and a keypad assembly (400) that comprises a sandwich of a static shield (430), button member (410), and switch contact member (450). The keypad assembly is assembled on the underside of the housing by means of a locating member (300) which has upstanding collar portions (325) that register in the holes of the face portion and depending pins (328) that register in holes in the members of the keypad assembly. The keypad assembly is held in place by a base member (200) that is joined to the housing and supports a raised pedestal (210) that extends into close proximity with the underside of the face portion and presses the keypad assembly against the face portion (FIG. 1).

Abstract: The computational processing power of a Digital Signal Processor (DSP) in linear-phase Finite Impulse Response Filter (FIR) applications is essentially doubled by taking advantage of either the even (symmetrical) or odd (antisymmetrical) symmetry of the response of such a filter.

Abstract: Unified messaging is a concept that provides for a single electronic mailbox for different types of messages. The mailbox can be on a user's host computer, PBX, PC, etc., and the user has consistant facilities available to originate, receive and manipulate messages. Messages can be translated from one media to another for reception, and a single message may be composed of parts that use different native media. The message recipient has a single controllable point of contact where all messages can be scanned and/or viewed.

Abstract: In a data transmission system using a predetermined trellis code, the output signal points are selected from a predetermined alphabet representing (k+n)-bit input words by using the values of n bits of each input word, and bits from previous input words, to identify a particular one of 2.sup.m subsets of the signaling alphabet m>n. The other k bits of the input word identify a pair of signal points of the identified subset. The sum of the components of one point of each pair is no less than zero and the sum of the components of the other point of that pair is no greater than zero. A running sum of the components of the signal points previously generated is maintained. If at any point in time the running sum is greater than zero, the signal point of the identified pair whose component sum is no greater than zero is generated, and vice versa. This scheme provides a channel-coded signal having a spectral null at dc.

Abstract: A data receiver which includes a timing recovery circuit or periodically adjusting a timing signal used to control sampling of the received signal is arranged to reduce or eliminate phase jitter introduced as a result of the adjustments. Apparatus and a method are described for forming a correction factor which is a joint function of the timing adjustment increment and a previous correction factor. Typically, correction is accomplished by forming the complex product of the in-phase and quadrature-phase components of the received signal and the recursively updated correction factor.

Abstract: In accordance with the present invention, local loop testing in an echo canceller based modem is provided in a manner in which proper operation of both the receiver and echo canceller can be assessed simultaneously. Specifically, the modem includes means for generating data and interfering symbol sequences and for applying the interfering sequence to both the echo canceller and the modem transmitter, while applying the data sequence only to either the transmitter or the echo canceller. During closed loop testing, the modem connection to the transmission line is opened, and a portion of the output of the modem transmitter is applied to the modem receiver via a leakage path through the hybrid. The received symbol is subtracted from the echo canceller output, resulting in application to the receiver of only a version of the data symbol sequence. Advanced knowledge of the characteristics of the data symbol sequence allows proper receiver operation to be verified.

Abstract: A system is disclosed for completing communication connections from end-users served by a connectionless (broadcast) type system in a manner which allows expansion of the calling area beyond the immediate physical limitations of the broadcast media. The system is based upon a device for mediating between the connectionless system and a connection oriented system. The device creates logical local area networks interconnectable by the connection oriented system. Calling user identification is used in conjunction with call completion data stored in a central memory for controlling all interconnections.

Abstract: Electro-static discharge is a problem with high-speed data even when using coaxial cables. Primarily, this problem arises at the terminal ends of the circuit where connections are made using separate coaxial cables for connecting to various pieces of equipment thereby allowing voltages to be induced differently in each such cable. This problem can be overcome by combining a portion of each cable such that the shield around each signal carrying wire remains intact while also being solidly in contact with the shield from the other wire. The cable is constructed by removing the outer insulation from a section of two single coaxial cables, electrically connecting together the exposed shields of each cable at both ends of the exposed section and reinsulating the abutted cables so that the shields remain in contact along their entire length.

Abstract: An I/O interface (24) couples a plurality of I/O devices (29) to a main memory (22) by way of a system bus (23). The I/O interface includes a plurality of buffer blocks (110) permanently associated with one or more memory pages (240). Each page is contiguous within the memory address spectrum and includes a plurality of memory blocks (230). Under control of a sequencer (125), the buffer blocks temporarily store data items being transferred between the memory and the devices. Data items being transferred between any and all devices and a particular memory page are temporarily stored by that page's associated buffer block and no other buffer block. The sequencer accumulates in a buffer block a plurality of data items being transferred by a device to memory by successive write requests, and causes a direct memory access (DMA) conveyance of the buffer contents to the memory upon occurrence of any one of a number of events.