From a previous (1/2009) thread on the subject of MicroChipping >>>

Quote:

Most vets have scanners available to read the most common systems out there:

There are also local microchip companies, which service a set geographic region.
Only vets in that area are going to have scanners which can read the chip.

- changing companies, find a vet who will use the microchip of the company you want,
and have a new microchip injected. Then register it.
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It's not a universal truth that "most vets" have scanner/readers!
Vets in SOME areas of the USA and Canada do have one or two of the MANY
brands and types of scanner/readers; but MANY areas, and some whole states,
do NOT have Vets, Shelters, nor Rescues that can read microchips!

Before spending money on microchipping a pet, make some phone calls to
area Vets, Shelters, and especially Animal Control - and ASK if they have
a scanner/reader and if they USE IT on all stray dogs and cats.
Unless a majority of the institutions have and USE a scanner/reader, the
probability of a lost pet being returned because of a microchip being detected
is pretty small.

As for having a "second" microchip inserted into a pet ...
I think that might cause some real problems!
If the microchips are similar in design and operating frequency, the TWO chips
might interfere with each other and give a meaningless indication on the
reader/scanner.

Lastly, here's a very lengthy discussion of the pros & cons of microchipping -
a must study for anyone who has or is thinking of purchasing pet microchips.

"Microchips & Your Pet" >>> http://home.att.net/~rfid/pet-chip.htm

/s/ Phred