Abstract: A video call distribution and method provides the user of a video station with access to a video network conferencing station without human operator assistance, even if the communication protocols of the user video station are incompatible with those of the video network conferencing system. Access is provided by remote user transmitted DTMF (or voice) signals, which signals are converted into compatible protocols in real time.

Abstract: Improved gain control is obtained in each receiver of a LAN interface or hub in a LAN of the type using amplitude critical signals for conveying information. An evaluation circuit compares a signal representing a calibration value to a predetermined limits and adjusts the gain by one of a plurality of amplification levels to maintain a high level signals which are more accurately decoded into digital information. Improved noise cancellation is also obtained by creating a primary copy and an inverted copy of the received amplitude critical signal, amplifying the primary and inverted copy signals by the same predetermined amount and adding the amplified signals. The addition reinforces the value of the received amplitude critical signal while effectively subtracting the noise effects.

Abstract: Multiple different operational capabilities, such as data transfer rates or communication protocols, are selectable for use on a single LAN. Enchanced nodes of the LAN have the capability of utilizing either an enhanced capability or a common capability in communicating with other nodes. Those basic nodes which are not of the enhanced variety have the capability of communicating utilizing the common capability. The enhanced nodes dynamically select the operational capability for the most efficient communication with other nodes.

Abstract: A transceiver for a LAN is capable of communicating multiple bits per signal element to increase the data throughput of the LAN. The transceiver includes a transmitter which receives a multiple bit digital input value originating at a node of the LAN at which the transceiver is present. The transmitter converts the multiple bit digital input signal into a pulse-like analog signal which is amplitude and phase modulated. A receiver of a transceiver at a receiving node the transmitted analog signal converts its amplitude and phase into a corresponding multiple bit digital output value. A time-domain filter of the receiver creates a primary signal from the received analog signal. To sample the primary signal at its maximum amplitude point, a derivative of the primary signal waveform is used to establish the zero derivative point at which the primary signal attains its maximum amplitude, and to establish a fixed sampling point for subsequent signals.

Abstract: Additional nodes beyond those permitted by the size of the address field of a standard network operating protocol, may be added to a directed token LAN, and the added nodes may be automatically and dynamically configured or reconfigured into a token passing loop. The added nodes, referred to as enhanced nodes, interoperably combine a standard reconfiguration sequence of a standard network operational protocol with an enhanced reconfiguration sequence of an enhanced protocol in order to send tokens to establish the next active nodes of the network and thereby establish the token passing loop through all of the standard and enhanced nodes.

Abstract: An output clock signal is synchronized with predetermined phase accuracy relative to an internal stable frequency reference clock signal upon the application of a transition of an asynchronous event signal. A plurality of phase shifted versions of the reference clock signal are derived. Upon the occurrence of the asynchronous signal, the states of the phase shifted versions are sampled, and that information is utilized as a code to select one of the phase shifted versions from which the output clock signal is derived. Synchronization occurs rapidly within the metastable settling time of the flip-flops of a register which sample or decode the states of the phase shifted versions, or by logical gating arrangements which avoid the necessity for considering the metastable signal. Synchronization is typically obtainable in less than the period of one reference clock signal.

Abstract: A video conferencing network for providing videos, audio, and data communication between remote video terminals. Each of the video terminals transmits and receives video, audio, and data information through the network. The network includes a central switching network for receiving audio and video information on one of a plurality of audio/video ports and selectively interconnecting this information to remaining audio/video ports. A centralized controller is in data communication with each of the video terminals and the switching network and controls the configuration of the switching network to provide the appropriate audio and video paths in response to the data received by the controller from the video terminals.

Abstract: Two different communication protocols are interoperatively combined for use in a local area network (LAN). An enhanced protocol can be selected as an alternative to a common protocol during communication between enhanced nodes of the LAN. Signals communicated between nodes of the LAN in the first and second protocols create the appearance of valid activity in both protocols, and always communicate at least some valid information in one of the protocols and selectively communicate additional valid information in a second protocol. Preferably the signals applied in the second or enhanced protocol include signals which are inserted in such a way that they are transparent to the first protocol. Improved network management capabilities and data transfer rates are available as a result of the information communicated in the second protocol.

Abstract: In a token-based local area network, the token may be selectively redirected out of its normal even rotational sequence among all of the active nodes of the network to pass the token more frequently through a priority group of nodes than through a non-priority group of nodes. The priority group is more likely to have messages to initiate from either a numerical or immediacy standpoint, compared to the non-priority group which is less likely to have messages to initiate. When token redirection is not desired, the token is passed in this normal even rotational sequence. Despite redirection, the token is still passed through all of the active nodes on the network in a periodic manner so as to assure normal network activity. Multiple messages can be initiated from a single node before the token is passed to any other node.

Abstract: An I/O network channel achieves relatively high rates of data communication between a plurality of widely physically dispersed devices interconnected by a LAN-type media. A processor connected to each node of the media controls the data and functions of a receiver and transmitter at each node to establish network level, transport level and session level data communication and control functions.

Abstract: A video conferencing network includes remote video terminals (10) interconnected to a switching network (66) through coaxial cables (16). The switching network (66) is operable to provide an audio and video data path between two or more video terminals (10). The switching network (66) operates as both an audio/video crosspoint switch and also as a network controller. In the network control mode, the switching network (66) operates in both a master mode for maintaining data communication with all of the video terminals (10) and also in a slave mode for maintaining status of devices attached to the switching network (66). In the master mode, the switching network (66) receives requests from each of the video terminals (10) and services these requests to determine available data paths for interconnection with other video terminals. In the slave mode, the switch (66) is in data communication with all of the video terminals (10) to determine the status thereof which is stored in a slave status table.

Abstract: An arbitration techique for a split transaction bus of a computer system obtains higher data throughput as a result of giving responders (e.g. memories) absolute priority over initiators (e.g. processors and I/O adapters), as a result of assigning all responders a higher priority than any initiator. Precedence is also given to retrying initiators which failed to complete a transaction because the module to which the transfer was addressed was busy. The requests from non-retrying initiators are temporarily rescinded to give precedence to the requests from retrying initiators. There is an absolute limit or bound to the number of requests which a retrying module may make before it is granted mastership of the bus to accomplish its transfer. To accomplish test and set and memory scrub transactions with a minimum time loss, the bus of the computer system creates a null conductivity cycle immediately following the cycle in which the address of the memory location to be tested and set or scrubbed is transferred.

Abstract: A multilevel communication structure controls input/output (I/O) data transfers and control functions in a computer system. Communication is achieved through shared memory structures in main memory commonly connected to each processor and each I/O adapter in the system. The levels of the communication structure are for communicating information between adapters or processors and processors, for communicating information relative to I/O control functions of an I/O device, and for specifying I/O functional operations. The information contained in the memory structures may be directly interpreted by sequencers of the I/O adapters, to achieve the I/O data transfers.

Abstract: An audio conferencing system includes a plurality of remote stations (10) which are interconnected in a conference mode through a central switching network (66) through communication lines (16). Each of the remote stations has a microphone (34) and a speaker (64) associated therewith. The microphone (34) on each of the remote stations has a voltage controlled amplifier (VCA) (59) associated therewith and the speaker (64) has a VCA (60) associated therewith. A CPU (48) selectively controls the output of the microphone (34) to selectively decrease the gain thereof when voice is not detected. When voice is detected above a predetermined threshold, the microphone (34) is allowed to operate at full gain and the speaker (64) has the output level thereof decreased. This effectively reduces the audio loop gain between remote stations in a conference.

Abstract: A video conferencing network includes remote video terminals (10) interconnected to a switching network (66) through coaxial cables (16). The switching network (66) is operable to provide an audio and video data path between two or more video terminals (10). The switching network (66) operates as both an audio/video crosspoint switch and also as a network controller. In the network control mode, the switching network (66) operates in both a master mode for maintaining data communication with all of the video terminals (10) and also in a slave mode for maintaining status of devices attached to the switching network (66). In the master mode, the switching network (66) receives requests from each of the video terminals (10) and services these requests to determine available data paths for interconnection with other video terminals. In the slave mode, the switch (66) is in data communication with all of the video terminals (10) to determine the status thereof which is stored in a slave status table.

Abstract: A workstation (10) for interfacing with a video conferencing network comprises a display (12) which has an internal camera (32) associated therewith. The camera (32) and various auxiliary devices such as a VCR (28) are input to a video switch (52) for selecting a video output. The video output is input to either a monitor (12) and/or to the network through an interface circuit (51). In addition, video can be received from a local processor (42). The monitor (12) operates at two video rates and can be switched therebetween by a CPU (48). The local processor (42) operates at a separate rate from the NTSC video of the monitor (12). A viewfinder (14) having a viewing surface smaller than the monitor (12) is provided as another output on the video switch (52) such that two displays can be received by the user at a given time. A microphone (34) and a speaker (64) are provided and controlled by an audio switch (54 ). This allows a full duplex audio path to exist between the network and the workstation (10).

Abstract: A dual mode, digital servo positioning system controls servo motor current by a processor-generated current control set point in conjunction with velocity feedback. When the motor has advanced to the vicinity of a target position, the processor opens the velocity feedback loop and reduces servo amplifier gain, such that the set point controls motor current without velocity feedback. This open loop condition provides a springy servo response that eliminates oscillation due to small deviations from target position caused by electronic drift or gravity. Position information is provided to the processor by means of quadrature encoded tachometer pulses from the motor.

Abstract: A lockbox is provided for a word processor printer output bin attached to a printer. The lockbox, which is insertable and removable from the output bin, is locked in the bin upon insertion, and can only be removed by disengagement of a first locking means. The lockbox has a security door which is positioned in a paper receiving position upon insertion into the output bin and which must be closed in order to remove the lockbox from the output bin.

Abstract: A digital information switching system features modular design with dispersed processing in which data is switched locally in one of a plurality of remote switching units for connection between local terminals, and data to be exchanged between terminals connected to different remote switching units is switched in a central switching unit, which is connected to the remote switching units by way of interswitch links. Both the central switching unit and the remote switching units are of the same general configuration being individually processor controlled. Reliability of each unit in the system is enhanced by diagnostic and maintenance features including provision of redundant devices in each unit, detection of device failures, automatic replacement of failed devices with redundant devices and communication of the failure to a remote service center.

Abstract: A scanning mechanism is provided for scanning individual output bins for receiving documents from a paper printer. The mechanism determines each bin's availability for receiving documents, the degree of fullness and whether or not a lock box is positioned in the bin for receiving designated documents.