Topic: What happens when external power to MT gets lower than 5 volts?

[Zonix]

Hello

My diy usb-battery box for Microtrack has six 1,5 volts batteries in series, regulated by a 5 volt (7805) regulator. Works ok. But I was wondering what happens the moment the batteries no longer supply enough power for the regulator and the voltage for MT drops below 5 volts? At which external usb-voltage does to MT change to the internal battery, or does the MT simply stop working until the usb-cable (with lower than 5 volts) is removed? Is it possible to mess up a recording due to external usb-power dropping below 5 volts?

Thanks!