u/JeSuisGourde

I'm reading a book about WWI and this question just popped into my head. How did individual British soldiers signal to each other that they were on the same side? Especially in the dark or outside of the trenches? Did they have code words or special hand signals or a whistle sound or something? In my hypothetical situation I'm imagining a lone soldier coming upon either a group or upon another lone soldier and signalling that they're friendly rather than the enemy. Was this even a thing? Would the approacher engage first to establish identity or wait til the other person asked who they were? I'm sure in the daylight you could tell by uniform and then by accent, but it seems like that might be a more difficult thing to suss out in the dark.

This morning when I unlocked my car it beeped a bunch of extra times but did unlock, and then the alarm started going off and wouldn't stop even when I hit unlock on my fob OR the car door. Eventually it shut off automatically. I've noticed the extra beeps when unlocking a few times previously. But the alarm has never gone off before.

Is this a fob issue? Electrical? Some door or trunk door or something not latched? I've never encountered this before.