EXFO FTB-500 - Manual (Page 20)

Introducing the FTB-500
12 FTB-500
Power Sources
Power Sources
Your unit operates with the following power sources:

Indoor use only: AC adapter/charger (four-slot model) or standard
three-wire power cord (eight-slot model) connected to standard
power outlet.
When it is connected to an external power source, the unit will
function even if the batteries are not present.

Indoor and outdoor use: Lithium-ion rechargeable batteries
(automatically take over if you disconnect the unit from its external
power source). The number of batteries that power your unit and that
come with it depends on the model that you have purchased. There
are two batteries for the four-slot model, and three batteries for the
eight-slot model.

Possible to switch from an external power source to battery power
or vice versa without affecting operation.

The battery recharges automatically when the unit is connected to
an external power source (with the AC adapter/charger or the
three-wire power cord).
For more information, see Electrical Safety Information on page 18.