Security interests for most types of collateral are usually perfected by filing a document simply called a "financing statement." You'll usually file this form with the secretary of state or other public office.
An assignee of electronic chattel paper may perfect by taking control. See Sections 9-314(a), 9-105. The security interest of an assignee who takes possession or control may qualify for priority over a competing security interest perfected by filing.
Chattel paper is a document used in secured transactions, like a chattel mortgage, confirming the buyer's and seller's rights and obligations.
Tangible chattel paper is sometimes delivered to the assignee, and sometimes left in the hands of the assignor for collection. Subsection (a) allows the assignee to perfect its security interest by filing in the latter case. Alternatively, the assignee may perfect by taking possession.
It follows that a security interest in a promissory note may be perfected by filing or by possession. However, perfection by possession of a security interest in a promissory note is preferable.