In a radio frequency communication system, a primary unit interrogates a plurality of secondary units over a radio communication channel. The primary unit receives a command to initiate an interrogation cycle over the communication channel. The primary unit then selects a time delay from a set of time delays, and transmits an interrogation request to each secondary unit of at least a subset of the plurality of secondary units in series after the selected time delay if the channel is free at the end of the selected time delay. The primary unit then selects the longest time delay for the next interrogation cycle if a channel grant command is received, and selects a shorter time delay for the next interrogation cycle if no channel grant command is received.

A method for data communication between a multiplicity of devices coupled to a LAN Bus without data transmission collisions. Each device is assigned a unique device address and a unique transmit time slot based thereon. The method involves responding to each data character received in each receiving device by loading a LAN.TIMESTAMP parameter with the CUR.SYS.TIME parameter. Thus the LAN.TIMESTAMP parameter indicates the time of the last data character when an incoming data packet terminates. Packet termination is declared when the LAN Bus is quiescent for a period after the last character equal to the PKT.END.DELAY value which is preselected. The method also involves determining whether the value of CUR.SYS.TIME represents a point in the unique transmit time slot for the device and then in response to determining that CUR.SYS.TIME is within the time slot, initiating the transmission of data if available, or otherwise, setting a new LAN.TIMESTAMP value. The method also involves invoking a transmit throttle after a device has finished transmitting a packet on the LAN Bus to provide fairness in LAN Bus access.

A multi-master serial bus system supporting, for example, up to 32 masters, and usable in applications requiring high-speed communications within a shelf. A plurality of nodes (2, 3, 4, 5) are interconnected by a highway (1) over which data is transmitted between the nodes. Each node has access control means (6) which ensures only one node accesses the highway at a time by means of an arbitration scheme. Data transmission involves an arbitration phase and a transmission phase and the highway comprises three lines, two of which are shared and perform respective functions in the arbitration and transmission phases (FIG. 1).

A method of arbitration for transmit mode access to the synchronous transmission medium of a distributed switching network whose architecture is based on a transmission medium time-shared between different stations, in which carries information in repetitive time positions, and in which a nominal time position being assigned on the basis of predetermined access criteria to respective stations communicating within the network, and spillover of stations outside the nominal time positions thus assigned is allowed. The arbitration method allocates an increasing access priority for an increasing seniority due to such spillover.

A process is disclosed whereby each of a plurality of stations, transmitting messages segmented into multiple sequential packets, is able to access a transmission channel of a local communications network. A residual packet number is associated with each message representing the number of packets remaining in the message after the instant packet has been transmitted. The number of packet collisions on the transmission channel is reduced by employing a resolution phase, which may be divided into several time intervals. Stations transmit messages with certain residual packet numbers during predetermined time intervals of the resolution phase. A station transmits its next packet after the end of the ongoing transmission if its residual packet number is smaller than the residual packet number of the ongoing message transmission.