BC9000
The BC9000 is a sign to manage anticollision system in intersection. It does not have routing layer and does not read destination address, making it usable in any rail circuit, not necessarily a ByteCart network.
It must be associated with any BC90XX sign (except BC9001), including another BC9000 sign.
This sign is placed on a branch that joins the main ring across an intersection, and is associated with another BC90XX on the main branch.
What BC9000 does is to synchronize its own lever with the lever of the associated BC90XX, giving 2 possible positions : ON-OFF or OFF-ON. Moreover the position can switch only if there is no risk to break a train.
Giving this rule, the preferred strategy of BC9000 is to switch off its own lever, giving OFF-ON whenever possible, providing that no train will be broken during operation.
On the other side, the preferred strategy of BC90XX is to satisfy routing layer, switching to the correct position (ON-OFF or OFF-ON) if necessary, providing that no train will be broken during operation.
On both sides, if preferred strategy can't be satisfied in order to avoid collision, one of the track will be deviated to alternate path. In other words, anticollision layer has priority over routing layer.
If address layer is not used, BC9000 signs can manage an intersection. Train feature is supported if a ticket is in the cart with train bit set.
A standard collision point (2 tracks become 1) can be managed entirely with 2 BC9000 working together in a ByteCart-unaware network.
Line #1 : Free
Line #2 : [BC9000]
Line #3 : Free
Line #4 : Free
The issue is to manage an intersection:
Carts must have an escape track that will be used when intersection is taken by another cart: on the main ring the escape procedure will be to turn left in the subring, and on the branch it will be to make a U-turn. The whole construction must form a 3x3 square.
When a cart comes from the left it powers off the lever. Carts coming from downward (if any) will be deviated.
When a cart comes from downward it powers off the lever. Carts coming from the left (if any) will be deviated.
The deviation track must loop. A router can do the job.
