Backplane type in topology table on 8600

[HungryHouse]

Hey all,
When a "show sys topology" outputs there is a field called "BT" which I found = Backplane Type.

I have mostly values of "12" for these but a few show "1"

Anyone know the meaning and significance/relevance of this field and its values?

Thanks much all,
HH

 

[GUFDK]

HI HungryHouse

I only faunt 1 box markt Bt=1 this box is a system 5000 and this box is using topology but is a old type nortel box and it's the only 1 not telling the passport remote port in the list

I think that Bt = type or vertion of topology but I'm not sure