English: Intermediate frequency (IF) transformer from a transistor radio receiver, with its rectangular aluminum shield removed. About 4 cm (1.6 inches) long. It consists of a polyethylene tube with two wire windings, one of them center-tapped, which connect to the the solder lugs on the bottom. Across both the windings are connected round ceramic capacitors, visible at bottom. In the center of the tube are two threaded ferrite magnetic cores. The cores can be turned with a hex wrench to adjust, moving them into or out of the windings, to individually adjust the inductance of each winding. Each winding with its capacitor constitutes a tuned circuit, which are inductively coupled, making a resonant transformer. The device acts as a bandpass filter in the radio receiver, filtering out the signals of unwanted stations while allowing the desired station through.