The customer would probably save even more money by buying the
manufacturered system like you are designing from the local radio-shack.
Or at least having you use their transmitter/sensor assembly's. The
transmitter units cost about 20 bucks apiece and just transmit an ident
code when activated, dont transmit when ok, this way a savvy burglar cant
transmit ok codes with more power than the remote units and fool the unit.
(although anyone can jam a rf based secirity system easily unless the
transmitters are spread spectrum.)

On Thu, 25 Jun 1998, Dave Miga wrote:

> HI!
>
> I've been contracted to design an inexpensive home alarm system using
> miniature transmitters (inside each sending module) and a matching
> receiver in the main unit. I've built a sucessful proto using Holtek 12
> bit chips (8 bit address to identify the sending unit, 4 bits to
> identify low battery, break-in, etc) and Ming RF modules. The customer
> wants to save money by eliminating the Holteks and using a cheap 16LC54A
> in the transmitter, and directly drive the 16C55 I am already using for
> the main alarm syscon. I probably need to move to a chip with more rom
> to fit both my alarm syscon code and a 12 bit serial code, but does
> anyone have any code already written for this application? Possibly even
> something similiar to a rotating code system like the Keeloq system from
> Microchip?    Thanks!    Dave Miga, Electronic Design Specialists
> http://www.eds-inc.com
>