Datapoint Corporation

William M Cox

Michael Andrew Fischer

Peter H Halpern

James H Nuckols

Floyd H McDougall

Larry W Koos

Charles Lawrence

John L Moschner

Plumbing fitting incorporating venting means

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.

LAN with dynamically selectable multiple operational capabilities

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. The sampling point is synchronized in phase with the stream of received analog signals. The residual intersymbol interference (ISI) effect of preceding signals on the LAN medium is eliminated prior to converting the primary signal to the digital value. To adjust and compensate for attenuation and amplification created by the LAN medium, the signal values are normalized.

Multibit amplitude and phase modulation transceiver for LAN

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.

Metastable-free digital synchronizer with low phase error

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.

LAN with interoperative multiple operational capabilities

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. Token redirection can be controlled in a predetermined pattern to accommodate either the actual or anticipated message traffic from the priority group of nodes, and can be controlled in response to a queue of messsages waiting to be initiated from a priority node.

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San Antonio, TX, United States of America

William M Cox