When assigning parts inside of AutoCAD Electrical, it automatically searches on the family type for the correct component type when assigning parts. This is based on the naming convention of the symbols so as an example a symbol with the 2nd and 3rd digits of the block name with CR will look at the CR table inside of the default_cat.mdb parts catalogue. AutoCAD Electrical has a pre-defined list of existing family types but the user is able to add their own:
How do you do this?
From the Project ribbon tab > Other Tools panel > select the ↓
Select 
Add Table to Catalog Database
Browse to the default_cat.mdb file. Typically on a standalone installation this is stored in the directory:
C:\Users\<>\Documents\Acade 2015\AeData\en-US\Catalogs
Select 
The dialogue will then show a list of existing tables within the parts database
Choose a table name of two characters. As an example
Table Name=PN
Table Description=Printers
In the above example, a new table specifically for printers would be created.
When closing the Symbol Builder (Block Editor) on completion of a new schematic symbol, you will then have this new table choice in the dropdown
This basically means that when assigning parts in a schematic, AutoCAD Electrical will only offer parts from the new table to the associated schematic symbol based on its 2nd and 3rd digit of its block name.