standby??
our type on the 738 only has "test, WX, WX/TURB/MAP positions on the unit box--
"TEST-
tests weather radar system operation-
allows test pattern and any fault messages on navigation display MAP, center MAP,VOR and APP modes, with WXR selected.
Note: if the airplane is on the ground and the thrust levers are not advanced for takeoff, WXR tests the predictive windshear system (PWS) indications...deactivating WXR on the EFIS control panel will NOT discontinue the test and can result in automatic WXR activation on both pilot displays. test last approximately 15 seconds."
only other switch is the EFIS Control Panel-WXR-"energizes weather radar 'transmitter' and displays weather radar returns--limited to 320 nm"
sounds as if some parts of the unit remain powered regardless of the various switch positions-and only the display or 'transmitter' itself is controlled by switches.