This is a Test Mode Switch, which is used in IC production (in case of using IC tester for measuring).
*If the bit of BUS is set as ‘0’, it becomes Test Mode. Then the test functions below will take active.
· Vertical Test
· E/W Test
· Tint Test
· Color Test
· Drive Test
· Contrast Test
Also, audio / video is muted forcedly.
* Usually, this bit is set as ‘1’ when the television is operating normally.