The Level Emitter

The Level Emitter emits a redstone signal depending on the quantity of an item in network storage.

There is also a version that emits a redstone signal depending on the energy stored in your network.

Items and fluids can be dragged into the slot from JEI/REI even if you don't actually have any of that item.

Right-click with a fluid container (like a bucket or fluid tank) to set that fluid as a filter instead of the bucket or tank item.

They are cable subparts.

Unlike other devices, level emitters do not require a channel.

Settings

The Level Emitter can be set to either "greater than/equal to" or "less than" mode
When a Crafting Card is inserted, it can be set to "emit redstone while item is crafting" or "emit redstone to craft item"

Upgrades

The level emitter supports the following upgrades:

Fuzzy Card lets the emitter filter by damage level and/or ignore item NBT
Crafting Card enables the crafting functionality

Crafting Functionality

If a Crafting Card is inserted, the emitter will be switched into crafting mode.

This enables two options:

The first option, "emit redstone while item is crafting", makes the emitter emit a redstone signal while your autocrafting is crafting some specific item through ME Pattern Providers. This is useful for only turning on specific power-hungry automation setups while they are actually being used.

The second option, "emit redstone to craft item", is extremely useful for specific use cases like infinite farms and automation setups that only have a chance of making an output, instead of a guranteed output. This setting creates a virtual pattern for autocrafting to use, for whatever item is in the emitter's filter slot. (For correct functionality, an actual pattern for the same item should not exist in your ME Pattern Providers)

This "pattern" does not define, or even care about ingredients. All it says is "If you emit redstone from this level emitter, the ME system will recieve this item at some point in the near or distant future". This is usually used to activate and deactivate infinite farms which require no input ingredients, or to activate a system that handles recursive recipes (which standard autocafting cannot understand) like, for example, "1 cobblestone = 2 cobblestone" if you have a machine that duplicates cobblestone.

Recipe

Crafting (Shapeless)