Abstract: The present invention helps derive accurate clock and carrier translation presets in the presence of noise and various line shapes. The invention provides an adaptive algorithm that optimizes the calculations of clock slew (.DELTA.T.sub.s) and frequency offset (.DELTA.f) over the specific line conditions encountered at each connection by choosing an optimal subset of the communication device's probing frequencies that minimizes the effect of line losses and noise.

Abstract: Multiplexer (100) includes a plurality of resident network management protocol handlers (116, 118 and 120). The multiplexer user can select which one of the protocols to use from among the resident protocols to use for framing network management messages received or transmitted via network management port (134). This selection can be made without requiring new hardware or software modules to be installed, and without significant run-time overhead to select among several supported protocols. Upon receiving a request to update the currently used protocol handler (116, 118 and 120) a handler index (124) which is used to select a pointer to all of the resident protocols, causes the newly selected to be activated, and any new network protocol messages are transmitted and received using the standards for the new protocol.

Abstract: Disclosed is a frame processing engine for receiving and processing a data frame having a header and a payload, comprising a first memory for receiving at least a portion of the header of the data frame; a second memory for receiving the payload of the data frame; and a controller, upon receipt of the data frame, for storing the header (at least most of it) in the first memory and the remainder of the data frame (including the payload) in the second memory, with the first memory having a shorter access time than the second memory.

Abstract: A data communication device (500) which is capable of providing inverse multiplexing, avoids having to perform address offset calculations by storing the incoming data from each of its incoming data channels in corresponding data buffers having predefined data structures which eliminate the need for offset calculations during data transfers and protocol processing. The communication device (500) compares the actual address location that a particular byte, such as a frame count byte, is presently stored in the data buffer and the address location it should be stored in order to avoid using offset calculations. If the actual location the frame count (FC) byte is located in is not the desired location the frame count byte should be located, the communication device (500) programs its SCCs (508, 510) to commence storing subsequent data bytes in the appropriate address locations in each of the data buffers found in memory (538) so as to avoid having to perform offset calculations during memory accesses.

Abstract: A fan support member (100) includes first (102) and second (104) cantilevered members extending from base member (116). In one embodiment, each of the cantilevered members (102 and 104) includes at least one retention member (106, 108, 110 and 112) which engage to corresponding recess locations (302, 304, 306 and 308) located on the fan (300). The cantilevered members (102 and 104) become loaded when a fan is placed between them causing them to press against the sides (312 and 314) of the fan (300) which helps keep the fan(300) securely attached. The fan support member (100) allows for quick attachment and removal of fan (300).

Abstract: Disclosed is a Digital Service Unit (DSU) which, in response to a digital signal from a Digital Data System (DDS) network, uses different techniques for different possible DDS services (include DDS-SC, CC64, and basic DDS services) to determine the type of DDS service providing the digital signal services and the line rates for such services. With respect to DDS-SC service, the DSU utilizes the fact that this DDS-SC service provides network defined frames of data to which the DSU tries establish frame synchronization at different line rates. The DSU also resolves the fact the DDS-SC service and CC64 service have the same 72 KBPS line rate by detecting the presence or absence of a control bit. For Basic DDS service, the DSU monitors the received signal for a plurality of possible invalid conditions. For each line rate, an error counter for that line rate is incremented each time an invalid condition is detected.

Abstract: The present invention provides a removable telephone line surge protection circuit (104) for use by an electronic deuce such as a modem (102). The line protection circuit (104) protects the modem (102) against telephone line surges such as those caused by lightning strikes. In one embodiment of the invention, the line protection circuit (104) interfaces with test circuitry which is preferably located within the modem (102) in order to allow the modem (102) to determine if the line protection circuit (104) is still operational while the line surge protection circuit (104) is connected to the modem (102). The present invention also provides for a removable surge protection circuit that is a testable module when connected to an electronic device having automatic module test capability as presented in one aspect of the invention. The surge protection circuit also provides for status indication of its operability in order to allow device users to make a quick determination of whether or not the module is damaged.

Abstract: In a Digital Data System (DDS) a method and apparatus for providing multipoint multiport service. Differences in time delays through the network are compensated by an alignment training wherein the delays from each remote station are measured at a Central station. The Central station determines how much delay to insert at each remote station and then instructs the remote stations to insert the delays. This allows all inbound data to be aligned in time so that when the data are combined within the network by the Multipoint Junction Units (MJU) data errors are not produced. Aligned frames are combined in the MJU operating in data mode in a logical AND operation so that marks transmitted by inactive ports are combined with data from active ports to produce a composite signal which is passed to the Central DSU.

Abstract: An Expert System 10 for providing diagnostics to a data communications network 5. Alarms from a Network Manager 24 are received and queued by an Event Manager 117 and then filtered by an Alarm Filter 118 to remove redundant alarms. Alarms which are ready for processing are then posted to a queue referred to as a Bulletin Board 120. A Controller 112 determines which one of the posted goals has the highest priority by considering a priority number associated with the goal plus a time of arrival of the goal. An Inference Engine 122 uses information from an Expert Information Structure 111 to solve the highest priority goal by a process called instantiation.

Abstract: In a Digital Data System (DDS) a method and apparatus for providing multipoint multiport service. Differences in time delays through the network are compensated by an alignment training wherein the delays from each remote station are measured at a Central station. The Central station determines how much delay to insert at each remote station and then instructs the remote stations to insert the delays. This allows all inbound data to be aligned in time so that when the data are combined within the network by the Multipoint Junction Units (MJU) data errors are not produced. Aligned frames are combined in the MJU operating in data mode in a logical AND operation so that marks transmitted by inactive ports are combined with data from active ports to produce a composite signal which is passed to the Central DSU.

Abstract: An Expert System 10 for providing diagnostics to a data communications network 5. Alarms from a Network Manager 24 are received and queued by an Event Manager 117 and then filtered by an Alarm Filter 118 to remove redundant alarms. Alarms which are ready for processing are then posted to a queue referred to as a Bulletin Board 120. A Controller 112 determines which one of the posted goals has the highest priority by considering a priority number associated with the goal plus a time of arrival of the goal. An Inference Engine 122 uses information from an Expert Information Structure 111 to solve the highest priority goal by a process called instantiation. The process of solving the goal may be interrupted by a pause or suspension in order to perform tests under the direction of a Network Test Manager 124 or retrieve other information during which time other goals may be processed.

Abstract: A technique for dynamically translating network management primitives into operations on management information stored within a relational database hosting a management information base. A CMIP network management operation and argument is retrieved from a network management processing machine and processed by a full or partial OSI stack. The CMIP operation is examined to ascertain a type of network management operation. If the operation is of a type which interacts with the database, a database query is generated in accordance with the operation type, to perform the network management operation on the relational database.

Abstract: A translator for translating objects defined in an object-oriented programming environment to a relational database schema permits persistent storage of object instances as records in a relational database. Object instances are mapped to entity tables with object instances represented by entity records. Simple attributes are mapped to primitive typed attribute columns and class valued attributes are represented by foreign keys into entity attribute tables. Derived attributes are represented by joins of the parent and child entity records.

Abstract: An Expert System for providing diagnostics to a data communications network. Expert information is entered using a user friendly User Interface which reduces need for the participation of a Knowledge Engineer. The User Interface including a template for entering a plurality of attributes for a hypothesis tree node. Among the attributes are an identifier for identifying a second node connected to the hypothesis tree node by a branch of a hypothesis tree. If the second node has not been defined, it is added to and displayed in a list of undefined nodes. Once all attributes for a template are completed, an identifier for the hypothesis tree node is added to and displayed in a list of defined nodes.

Abstract: A translator for translating objects defined in Abstract Syntax Notation such as ASN.1 to a relational database schema permits persistent storage of object instances as records in a relational database. Object classes are mapped to entity tables with object instances represented by entity records. Simple attributes are mapped to primitive typed attribute columns and package or group attributes are mapped to separate dependent entity tables. Derived attributes are represented by joins of the parent and child entity records.

Abstract: A data modem is provided with a boot ROM having a set of instructions for a programmable processor to perform its basic functions within the modem. Enhancements and firmware updates are downloaded over a telephone line through the modem's inherent communications abilities and stored in a battery backed RAM. This permits firmware updates and enhancements to be implemented remotely without need for replacement of ROM or opening of the modem housing.

Abstract: A dialed telephone connection can be implemented as an end-to-end digital connection by virtue of switched voice transmission facilities becoming more prevalent. If such a connection is detected, it is possible to transmit digital data over the connection at a much higher rate than using analog technology. A dialed voice call is emulated to set up such a connection and the connection is then tested to determine if it is end-to-end digital. If so, high speed digital data can be passed. If not, the connection is broken and then reestablished repeatedly until such a digital connection is found. In one embodiment, the calls are alternately initiated from each of the two parties involved in attempts to increase the likelihood of achieving an end-to-end digital connection. If no such connection can be obtained after a reasonable number of tries, an analog communication session can be established.

Abstract: A switched digital circuit is used to restore a failed dedicated digital circuit to a remote station in conjunction with reconfiguration of the network's multipoint junction units (MJU). A circuit is established over the public switched digital network from the customer's central location to a remote station requiring restoral. The remote station is then connected back to the dedicated multipoint circuit, at the telephone company central office facilities, by way of digital cross connects and MJUs that perform the digital bridging. The switched digital access line, from the customer central location to the telephone company facilities is then available for use in establishing switched connections to the other remote stations. The process is sequentially repeated for each dedicated digital circuit to a remote station to be restored, thus conserving hardware required at the customer premises and minimizing the number of dial up switched digital access lines needed at the customers central location.

Abstract: The present invention is directed toward a method and apparatus in a communications device for mapping a selected group of data bits into a predetermined number of two-dimensional symbols selected from a minimized alphabet of M two-dimensional symbols forming a symbol constellation, with one of the two-dimensional symbols being transmitter during each symbol (i.e., baud) interval. A plurality of symbol mappers in an adaptive communications device use a superframe of bits per baud. Each superframe includes at least two groups of frames, a low bit frame and a high bit frame. The superframe has A) one of these two types of frames uses whole bits per baud and the other uses fractional bits per baud or B) both of these two types of frames will use fractional bits per baud.

Abstract: In a data communication network, a method and apparatus for determining routing in a diagnostic channel utilizes a search token which is passed through nodes of a memory model of the network. The memory model represents nodes as one (or a combination of) object models representing aggregation, deaggregation, mesh or translation operations. By referring to a relational database, selective searches are performed without need to flood the network with search tokens. The search results may be displayed graphically for easier understanding. The method also has general application to a relational database management system by allowing for display of the database relationships and interconnections in a graphical manner for easier interpretation by the user.