What are the necessities of a door alarm?

[OsMaN_93]

I'm making a door alarm, what MUST it have?

I already have; low cost, easy to use, brightly colored/visible, not too small or big (to act as a deterrent)
can you suggest some more please?

 

[HarveyH42]

Need to give more details on what you want. What type of door? There are many to choose from, best I can guess, is that it's not a car door...
What do you want it to do when activated? Signal an alarm system, ring a bell, sirens, flashing lights, electric shock, explosion?

How do we know how much you want/need? Don't want to go overboard, and you aren't happy with what you already have. No way to gauge just what is best for you application. Is this for home, business?

 

[audioguru]

Simply move away from the poor area that has thieves and murdurers to a better area that has normal people.
My neighbourhood has no crimes.

 

[HarveyH42]

If the warm weather stays up there, I might sneak across the border...

 

[OsMaN_93]

its a simple bedroom door alarm, I'm not an electronics genius, so you can't expect much of me

it has a siren when trigered.

 

[mneary]

An alarm itself isn't a deterrent. People have to think you have an alarm. The alarm itself is optional.