Erm? What exactly is a "bobbin"? And a "rectifier"?
The term "bobbin" refers to the shape of old cotton reels, and in this case is a small rubber mounting with a male screw thread at each end. You poke one end through a hole & screw a nut on, that sort of thing. Used for mounting things onto vibrating surfaces & thus isolating the vibration to the attachment.
The "rectifier" is a device that converts AC current to DC. More
here 
