A method of transmitting data on a communications network having two oppositely directed unidirectional buses (A,B) and a number of access units (4) coupled between buses, the method including the step of establishing a queue which is distributed in the access units and which controls when the access units can transmit data packets on the buses. When an access unit has a data packet (38) queued for transmission on bus A, it sends a REQ bit on bus B. The access units monitor the number of REQ bit...

A computer network method and apparatus. The present invention comprises a computer network having one or more hubs, each hub comprising one or more connection means for connection of computing devices to the network. Each connection means comprising a first interface means for coupling with a computing device, a second interface means for coupling with the network and a protocol processing means. The protocol processing means receives message packets and, depending on the message type, processi...

A method of communicating between two control units includes transmitting a message from one control unit to the other, checking the message at the other control unit for proper reception, if the reception is not proper, sending a NAK signal from the other to the one control unit, if the reception is proper, sending an ACK signal from the other to the one control unit, and upon receiving an NAK at said one control unit, resending the original message.

A method of transmitting data on a communications network having two oppositely directed unidirectional buses (A,B) and a number of access units (4) coupled between buses, the method including the step of establishing a queue which is distributed in the access units and which controls when the access units can transmit data packets on the buses. When an access unit has a data packet (38) queued for transmission on bus A, it sends a REQ bit on bus B. The access units monitor the number of REQ bit...

A protocol system for data processing equipment, particularly equipment used in building automation monitoring and control systems for air-conditioning control and monitoring of fire and security points is disclosed having a plurality of stations connected to a data bus, each station having an apparatus for monitoring the traffic on the data bus, calculating its turn to transmit or time slot during which it is permitted to transmit data on the bus and updating its calculated turn or time slot af...

A transceiver circuit for connecting a data processing unit to a communication bus, wherein said data processing unit is capable of transmitting, receiving and processing non-return to zero (NRZ) signals having a normally high level and assuming a low level to indicate a data bit and said communication bus is capable of transmitting a pulse-no pulse signal to indicate data bits, is disclosed having an input connected to the data processing unit for receiving the non-return to zero signals, a tri...

In communication which uses a communication line which allows the determination of a communication protocol in a communication port prior to the communication like in an ISDN network, a communication program corresponding to the determined communication protocol is dynamically linked and initialized to allow dynamic selection of the communication protocol.

A telecommunications terminal is provided with two protocols. After initialization and activation of one of the protocols, a status inquiry is sent to a digital exchange indicating the activated protocol. The telecommunications terminal is operated according to a received status message indicating the protocol being used by the digital exchange, or if none is received before elapse of a timer, according to the second of the two protocols.

A protocol analyzer is provided for monitoring a selected communication connection being conducted in accordance with a predetermined protocol by the exchange of protocol data units between two entities over a data network. The analyzer includes a monitoring device for identifying protocol data units, a protocol-follower conditioned in dependence on said predetermined protocol and operative to follow the progress of the connection as it receives relevant protocol data units from the monitoring d...

A method of transmitting data on a communications network having two oppositely directed unidirectional buses (A,B) and a number of access units (4) coupled between buses, the method including the step of establishing a queue which is distributed in the access units and which controls when the access units can transmit data packets on the buses. When an access unit has a data packet (38) queued for transmission on bus A, it sends a REQ bit on bus B. The access units monitor the number of REQ bit...