On Mon, 20 Apr 2015 20:45:28 +0100, Andy Burns
wrote:

MM wrote:
I want to hear an alarm sound/see an LED flash when the postie posts
something through my letterbox.

I'd say use an alarm contact with its magnet as your trigger, e.g.

https://securitywarehouse.co.uk/catalog/-p-2544.html

Or put a post-it note on the door asking the postie to ring the doorbell
whenever they deliver something :-)

Not sure whether he can read... certainly dozy enough to deliver the
wrong mail to me, or my mail next door sometimes. Plus, not ring the
bell when necessary. Once he handed me a packet that clearly needed
signing for, so I asked, shall I sign then? And he said with a grin,
nah, that's okay. Couldn't be bothered to dig out his doubry and
stylus. (Maybe he'd forgot to being it.)

MM