Sony SSM-121 Below you will find brief product information for Sony SSM-121. This 12-inch black and white monitor can be used as a closed-circuit television monitor or a video preview/playback monitor. It features a loop-through connection that allows up to three monitors to display the same picture. The electronic circuits provide safeguards against interference, noise, and changes in signal level to maintain a clear and stable picture. The monitor has composite video inputs and outputs, and its video input impedance is 75 ohms terminated.