Whistle in your torch or backpack

One of my friends asked me to write this as not everyone is aware.

There are whistles build in headlamps and backpacks.
Almost everyone has it, not everyone knows it.

You can ask “Why do I need whistle ?”.
In theories this is emergency device – I personally don’t believe if this is useful in emergency situation.

I used whistle once.
We were setting camp near a river in a deep valley.
There was no easy and visible access to the river.

I took one bottle and went down to find best approach to collect some water.
At the time I found proper place I used whistle to inform the rest of our group that someone can go down with the rest of our containers.

I can imagine more cases like that.

Reason was to use minimal amount of energy to maximise effect.

Whistle was just there – waiting for usage.

Picture – whistle in headlight.