On Mon, 17 Dec 2012 15:23:52 +0000, Roger Mills wrote:

Recently received an email from LocksOnline (from whom I've bought
mechanical bits and pieces in the past) attempting to sell me a security
system. Details he
http://www.locksonline.co.uk/acatalog/
Alert_Pal_Alarm_Camera_Home__Fire___Security_.html

The idea seems to be that when (if) it detects an intruder or a fire in
your home, it sends you and SMS message - together with photos of
whatever its camera can see - prompting you to contact the police or
fire brigade from wherever you happen to be.

Anyone come across this sort of system? Would it actually work?

I ask partly because a thread started by Bill Wright in another NG
seemed to suggest that SMS message may sometimes not be delivered for
several hours. If that were the case, your house may well have been
cleared or razed to the ground by the time you knew about it.

SMS, like email, is inherently unreliable. It's not guaranteed to work,
and in instances where it doesn't the originator may not be aware of it's
failure.

If you want reliability, you need to add another layer of protocol on
top, to deal with acknowledgements and the like.

In a previous role, I added a feature to our emergency logging system, to
generate an SMS to the assigned engineer. I made it crystal clear at the
time this was simply an addition to help the engineer by having the
postcode on his phone, rather than having to call into the office for his
next call. Of course within 5 seconds they ignored that, and started
bitching when SMSs weren't received. Unfortunately for the helpdesk
staff, the front page of the training manual I prepared had in block
capitals a disclaimer that the SMS feature was not reliable, and they
should tell the engineers as much.

You can get secure messaging services. Another employer I worked for used
"Cognito" which allowed for delivery and read receipts. It was integrated
into the ticketing system, so we could work out how efficient the
engineers were - they hated it as we could tell exactly when they opened
a message. I think it was overlaid on the GSM network.