This is the most versatile CCTV test monitor on the market. It's manufactured by Wonwoo Engineering (www.wonwoo.com) the originators of this type of tester, and it's supported by their facility in California. Building on the success of their RAPPORT 337, and Rapport-II CCTV testers, Wonwoo engineers have completely redesigned the circuitry to increase battery run time to more than 7 hours and replaced the analog display with a sharper all digital LCD display.