When a pedestal sends items to another pedestal, it 'asks' that receiver pedestal if it can accept the items. If the receiver pedestal has a filter upgrade in it, the receiver checks the inventory below for any matching/allowed items, and will reply to the sender with a yes or no if it can or can't accept the incoming items

The exception is the Filter Food, Filter Enchanted, and Filter Enchant Count that do not require inventories below.

So basically if your using filters, youll need 3+ pedestals linked together to make it all work.

• One Pedestal to send a stream of items needing filtered. (an import upgraded pedestal on a chest full of ores for example)
• One Pedestal upgraded with a filter and an inventory below it with single items in it to act as the 'filter', this should be linked to the import pedestal first.
• One Pedestal connected to the filter upgraded pedestal to receive the filtered outputs.
• Another Pedestal connected second to the import pedestal to catch any items that dont match whats being filtered. (sometimes items that should have been filtered will sneak into the second pedestal, this is only because the filter pedestal was full at the time the import pedestal tried to send the item)