Question:  Is it possible to disable either Channel A or B on a WTR-680 beltpack? 
Answer:  Yes this is possible via the beltpack menus. Use this procedure:
• Press and hold [SET] then press the [CHAN] button to
show the channel enable/disable screen. The current set-
ting of the feature is displayed on the LCD.
• While continuing to hold [SET], press the [CHAN] button
again to move to the next option, only channel B on.
• As you continue to hold [SET], press the [CHAN] button
once more to move to the next option, only channel A on.
If the channel button was hit once more, the user would
start over at the AB ON screen.
• Release the [SET] but ton to accept the current displayed
setting and return to the Group/Channel screen.
See attachment below for instructions with pictures of the display.