Prime Computer Inc.

Thomas C Hogan

Richard G Bahr

Arnold Adelman

The invention features a method and apparatus for improving data transmission in a transmission system having an analog signal transmitter directly connected along a transmission link to an analog signal receiver having a threshold element for detecting the signal. The invention features clamping voltages appearing at an input of the receiver symmetrically about a threshold value of the threshold element.

Data transmission signal apparatus

An apparatus and method, for connecting a node to and disconnecting a node from a high speed data communications network, has a dead man switching element and high speed solid state switching circuitry interconnected therewith to avoid the effects of mechanical contact bounce normally associated with operation of the mechanical switching element. Thereby, massive data losses on high speed communications paths, and token loss in a token-passing ring network, are substantially avoided. The switch has the solid state switching circuitry connected both in parallel and in series with its mechanical contacts for providing node isolation and communications path bypass channels during the time that the mechanical switch bounce occurs. The alternate paths are maintained during a change of state of the mechanical device, that is, when the node is being connected or disconnected from the communications network.

Bypass method and apparatus for debouncing a mechanical switching

A communications network including a plurality of terminals coupled together to provide a unidirectional communications ring. Each of the terminals is coupled in series along the ring. Each terminal is adapted to transmit (at an associated data rate) a digital signal to the next downstream terminal on the ring. Each terminal is adapted to receive a digital signal at the data rate associated with the next upstream terminal. The received digital signal is applied to a phase locked loop characterized by a hold time which exceeds its lock time. The phase locked loop extracts a local timing signal for re-clocking the received digital signal. The transmission time of N bits is less than the hold time of the phase locked loop. Each terminal monitors the re-clocked signal to identify when same valued consecutive bits are received for a period less than the phase locked loop hold time, and upon such detection to cause that terminal to generate at least one transition.

Self initializing phase locked loop ring communications system

A communications network including a plurality of terminals coupled together to provide a unidirectional communications ring. Each of the terminals is adapted to transmit (at an associated fixed data rate) a digital signal to the next downstream terminal on the ring. Each terminal is adapted to receive a digital signal at the data rate associated with the next upstream terminal. In each local terminal, there is a detector for detecting the received synchronization packets and associated data packets are generated for transmission to the next downstream terminal on the ring at a predetermined fixed data rate associated with the local terminal. The data of each transmitted data packet matches bit for bit the data of the corresponding received data packet. The number of bits in the transmit synchronization packet differs from the number of bits in the associated received synchronization packet in a manner so that the data rate for the composite packet formed by the transmitted data packet and associated synchronization data packet corresponds to the transmit data rate for the terminal. The difference varies between predetermined minimum and maximum limits, and may be zero for two terminals having substantially the same transient bit rate.

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Natick, MA, United States of America

Thomas C Hogan