ProNET variation – Start topology

ProNET variation as star topology is as shown below –

The 3 hosts are connected logically by a ring connection and physically by a start connection via a wire center. The wire center consists of relays R1, R2, R3, R4 so that the relays connects the corresponding host to the wire center via the interface. Th relay R3 is not connected to any host. The relays receives  power from their respective hosts. Relay R3 doesn’t receive power from any hosts.

When any of the hosts say H4 is in transmit mode and sends the data to H2, the electrical signals are sent from H4 via the relay R4 to interface of H1 via R1, back to R1 and then to H2 via R2 and interface of H2. The relays are powered by dc power from the hosts and the wire medium separate the dc from ac signals.

The ProNET 10 interface hardware comes on two boards for the ProNET topology to increase the reliability . They are the controller that can perform and participate in copy and token recovery mode without help from CPU and a computer interface that depends on CPU to read or write packets. The use of two boards isolates the rest of the network from the OS failures of a given packet.