What the use of `horn`?

[lockie]

During the next countless adjustments of the KV-1, I bumped into parameter `horn`. This is a signal, when u press `H` button at the driver place.

//signal sound
snd_horn=horn;

I played a large number times in SF, but didn't meet any use of this `horn` Perhaps, we should use it during attack to scare the enemy?