Press PGM then F3 (GLOB) to get to the Global Settings Menu.
AttenMode: This setting controls how the attenuator is applied to the objects in the radio. The attenuator reduces the amount of signal at the receiver input and helps reduce interference from strong nearby transmitters.
Normal - the attenuator follows the individual object attenuator setting.
Global - applies attenuation radio-wide (see Global Atten), regardless of individual object settings.
'G' will appear in the display when scanning or searching.
Note: You can also do this by pressing FUNC then ATT in Scan or Search mode.
Global Atten: When set to 'On', turns the global attenuator on only when AttenMode is set to Global.
'A' will appear in the display when scanning or searching.
Note: You can also do this by pressing ATT in Scan or Search mode.
Taken from:
Easier to Read Pro-106/197/PSR500/600 Digital Scanner Manual