LG M4210LC Owner's Manual page 44

RS-232C
Transmission / Receiving Protocol
03. Aspect Ratio(Command : c) (Main picture format)
To adjust the screen format.
You can also adjust the screen format using the ARC
(Aspect Ratio Control) button on remote control or in the
Screen menu.
Transmission
[k][c][ ][Set ID][ ][Data][Cr]
Data 1 : Normal Screen (4 : 3)
2 : Wide Screen (16 : 9)
4 : Zoom1 (AV)
5 : Zoom2 (AV)
6 : Original (AV)
7 :14 : 9 (AV)
9 : Just Scan(HD DTV), 1 : 1 (RGB PC, HDMI / DVI PC)
Acknowledgement
[c][ ][Set ID][ ][OK][Data][x]
04. Screen Mute(Command : d)
To select screen mute on / off.
Transmission
[k][d][ ][Set ID][ ][Data][Cr]
Data 0 : Screen mute off (Picture on)
1 : Screen mute on (Picture off)
Acknowledgement
[d][ ][Set ID][ ][OK][Data][x]
Controlling the Multiple Product
A6