Ah, indicators!
I used lots of different non electronic in my early years. The most memorable being budgie bells tied onto monkey climbers. The least memorable was the sweetcorn lid folded in half. When I struck it instantly cut the line!
First electronic alarm was a Rolon, absolutely terrible it was and I replaced it with a pair of maladjusted Herons with a very unique sounder box. Bamford style Optonics were next, then Super XLs. My last ones were Fox MMXs which I found virtually bombproof. That was about 20 years ago and they are still going into meltdown for me! The only fault I have is that one of them has lost the two tone drop back differential which I find really useful, instead it just gives out a normal bleep. Amazingly, I found the boxes in the loft a couple of weeks ago, £59.95 each. That’s a lot of money let alone 20 years back!