Unlike the mortgage pass-through securities, the mortgage-backed bonds are debt obligations of the mortgage originator. Every issue of such bonds should be backed by a pledged collateral. A property that can be pledged as security for mortgage-backed bonds is called eligible collateral and is described in each indenture. Eligible collateral includes cash, government securities, federal agency certificates and high-quality money market securities. The bonds are secured by a first charge on each item of pledged collateral that is assigned and delivered to a trustee to the issue.