Re: Why are restaurant RF gizmos so complicated?

Hello AutoTracer,

The garage door opener thing is a transmitter not a reciever.  Transmitters
are generally simpler electronically.  You really can't compare that to a
restruant pager.  Check out the electronics on the inside of the opener and
you have a better example but even then the signaling method is likly
different as well as the frequency band making it hard to compare the
demodulation section.


I did compare it to door receivers, like those inside the Genie motor boxes.

These restruant recievers are just repackaged pagers and may be signalled
locally or from a cell tower like arrangement already existing to serve
pagers.  Thats why they work when you wander off to the mall way across the
parking lot.

Pagers have been around for years and as such may have a whole range of
complexity from low to high integration.  What you saw may not be
representative of the cutting edge which would be likly more expensive than
a well established product using parts that have been around for a while.

Maybe it wasn't cutting edge but I have seem similar ones. They contain a lot more parts than a pager. That's what is puzzling.

Even a highly integrated (1 chip) reciever/decoder would still be rather
complex inside as the reciever has to demodulate a digital signal from an
analog carrier then decode its contents to determine if the message is for
that unit or not before vibrating.  Though not on these units, the chips may
also support LCD display for text messages but not inplemented.

One-chip solutions are standard now, from several vendors. They don't need nearly as much in discretes around them compared to what this restaurant pager did.

If you think these recievers are not made cheaply enough, consider that
clear plastic cost less than colored plastic for the case (assuming non
recycled virgin material)

Usually black and some other dark ones are cheaper, at least when we did them. Clear has more rejects after injection molding, you see every speck of contaminant. Basically the plastics guys showed us a color palette and it all cost the same. The minute we wanted something custom it got really expensive. Then, in one case, marketing finally agreed to a standard color: Purple! Yechhh. The downside was we had to buy several tons of granules.

Regards, Joerg

http://www.analogconsultants.com
.

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