Low-Battery Warning; Critical Low-Battery - Fisher F-Pulse Owner's Manual

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B TTERIES
The F-Pulse operates on 2 AA alkaline, lithium or nickel-metal
hydride batteries (not included).You can also use high quality
rechargeable batteries. Expect approximately 25 hours of
operation from alkaline batteries.
Do not use "Zinc-carbon" or "Heavy-duty" batteries.
To replace batteries:
1. Use a coin or flathead screwdriver.
2. Rotate counterclockwise to remove cap.
3. Install 2 AA batteries, positive-side down.
4. Rotate clockwise until snug to close and seal.
The battery compartment was designed to provide a snug fit
for the batteries. If you experience difficulties in removing
your batteries, tap the pinpointer against the palm of your
opposite hand to help dislodge the batteries.

Low-Battery Warning:

If your batteries are running low and need to be replaced,
you will hear a boop-boop-boop sound at power-down.

Critical Low-Battery:

If the batteries are totally spent, you'll hear a boooooop
sound and the pinpointer will then turn itself off.