A system for determining polarization of a gas comprises a container that contains the polarized gas. The toner density of a pattern, which is formed on a supporting member in the image forming apparatus, is calculated based on a sum of the amounts of specularly reflected light and a sum of the amounts of diffusely reflected light. In one variant, the connector further comprises a plurality of electrical components including an integrated circuit adapted to condition the signals being transmitted over the cable. Accordingly, the color display with good color balance can be realized.