Coexistence of LF HDX systems

Hello Colin.

Nice work Colin...we too investigated collision avoidance strategies for HDX...what a fine way to end this year.

Your concept of "stealth adaptation" is useful for us to reflect on and we shall.

We use short power (15mS) pulses to detect "Near" tags and long pulses (100mS) for "Far" things.

We also experimented with "step change" power field intensity to trigger distant tags long before the close tags were triggered to reply.

We also experimented with "frequency shifting" partway through the power field durance to separate things into "near and far".

The concept of FM capture effect is a powerful phenomena to work with. We cannot change the tags but we can 'Adapt the Reader(s).

We also use arrays of listening receivers that are spatially unique to the passing cattle...we call this concept our "massive array chorus".

We only deal with RO Tags, so clever arbitration algorithms are not available and like you we explore other ways to read all simultaneous present tags (within the detection volume). I assume you have synchronized all other "On-site" Readers through a copper connection!

We build on the theme of chaos and conditional invisibility in our thinkings, if all tags ceased moving then we reason if you can't move the cows the "move the field"..these are adaptation mechanisms we employ, much as you have done by forcefully controlling the behaviour of the tag...

In your application it seems acceptable to hand modify each tag with a "time out over-ride"...it may be useful and easier for you to use shorter pulses and desensitize the Reader-receiver to shrink the "detection volume" for "single file animals"? ... the HDX concept was probably only thought to be only used for single animals, however we must make it useful for simultaneously for "crowds" of animals.

Is the figure 38mS a "magic figure" or was some science used to determine it?

It is highly unlikely I will abandon LF HDX, though it may licence it off to others...some aggressive inroads are now being made by UHF "cattle systems"...undecided countries still debate FDX/HDX/LF/HF/UHF etc...every cow in Australia now has LF-HDX..."if logic" prevails the rest will follow.

TI have tightened up their manufacturing tolerances with the introduction of HDX+... the huge variation of older tags was truly technically challenging and embarrassing , for them to leave the scene is almost inconceivable.

"Stealth" is another form of conditional-invisibility, may we use/borrow your terminology? ...we will watch your innovative works.

Regards

Ray

Thanks Ray for your interesting and informative reply.

Yes the 38mS was chosen for two reasons:

1) The timing circuits are analogue and are variable in production due to MOSFET  source/gate threshold variations.  38mS allows headroom to absorb these tolerances.

2) More specifically the 38mS is 20 mS + 15mS + 2mS since we load our IDs post production and we have to get round the extra write charge time of around 15mS.(We use 20mS Charge Phase)

The technique harvests power from the inlay pickup coil and usesextremely low power to avoid compromising the inlay tag range. It does reduce it by a couple of centimetres but our access application can accept that. In assembly we use 1mm nylon washers to standardise the physical distance and therefore the mutual inductance twixt the coils. We epoxy pot the Stealth Key in a disc not much different from the W9QL package.

The ownership of the Stealth Tag are American Calan of Northwood N.H. and I will talk to them about co-operation with T.I.

I chose the LF HDX system because of my very long term experience of FSK in short wave communications starting with Army RCA transmitters in Malta in 1955/6 in teleprinter links to Libya of all places , so the merits of FM signal capture and noise survival appealed to me ! (Aso FCC lab testing was a dawdle). the theory is sound in all situations where the external system uses the 50mS or greater power phase.   In the production model I have played safe by using a trimpot to set the 38kHz and a header shorting link to disable the Stealth mechanism during ID writing - as a safety measure. Our IDs provide an addition CRC and Mfg code with the 64 bit code space  just to make absolutely sure that no animal can gain false entry. The product is the Calan-Broadbent feed door which has been in use in the USA since 1970.  As a long retired engineer who developed this system I decided to bring it into the 21st century in a conservative manner. The T.I. LF-HDX is a very robust and cost effective system and the  lamented departure of the RI-TRP-W9QL-30 just as we were manufacturing the first product in New Hamshire rather dinted faith in T.I. and makes me very nervous about the TMS3705 which has been an entirely trouble free technology for this application and easy to manufacture inmodern assembly facilities.

Further to the experience at a Nebraska USDA facility and the absence of co-existing problems, I hear that the other equipment provider uses a dual standard reader and I am suspecting that their tags are Mifar which of course would not look for the post power phase signal. I may be wrong but that seems likely.

I will get back to you after I have talked with AMCAL in Northwood.

As I said, very many thanks for your generous exposee on co-existing  concepts.  Our Stealth Key works, but just how high the yield will be in production remains to be tested. - it certainly gets us round co-existence with LF-HDX Dairy Parlours.

Best regards and a Happy Xmas.

Colin -  Edinburgh - Scotland.

Gents, great discussion.

I am very much impressed with your deep technical knowledge and your innovative approach to improving your systems.

I willl have someone closer to the current ISO activities comment on future features (such as anti-collision) for animal ID that are currently under discussion in the ISO forum.

As for the TMS3705, there are currently no plans for obsolescence. Also, TI stays committed to LF HDX and is eagerly working on expanding the HDX footprint in the RFID world.

Have a great new year!

Klaus Seiberts

Thanks Klaus,

Grateful for you comments and relieved to hear about the TMS3705 being relatively safe forthe time being.

The Stealth discussion will be ongoing to advance our thinking !

Happy New Year

Colin

Hi Ray,

I did not respond to your sync enquiry relating to our multiple reader deployments in our Calan/Broadbent door installations.

The upgrade TMS3705 readers have to replace our legacy "Grid Dip Osc" system so running a sync connection was problematic.   The readers are placed generally 1 metre appart along the feeding fence but we do also provide calf installations with spacing about half this so a solution had to be found to adjacent power phases resting on a read 15mS period.

What I did was to introduce a random element into the repetion cycle instances so thay there could only be randon implications which would tend to last for only one cycle. Our animals are a pretty intelligent lot and if the do not hear our system locking bolt clicking , they realise that they must try again or simply wait in the field until the next scan (randon 3 per sec)powers the key.  This coupled with a well defined ferrite antenna field makes it most unlikely that the animal will even know that a cycle has been missed.

This works entirely to our satisfaction and there have been no incidents on site to suggest that animals or indeed customers know that this is going on (except for the technically interested customers). On the lab bench reliable function was sustained down to about 30cms.

This probably would not work in a walk though system since missing a scan might mean a scan mist.  Selecting a reasonably fast scan rate and long antenna might handle this. The scan instant shifts randomly about 30% , I think since this parameter was set empirically.  The initial no random situation allows adjacent door to creep slowly through their phase differences and could virtually kill detection at 30cms.  It seems to work rather well but we only have a few hundred of the upgraded doors in use. Logically however simply avoiding multiple scan cycle blocking over consequetive scans suits us.

You will have deduced that 20 +15+ 3 =38mS (A typo in my last response).

I am getting a further 40 Stealth Keys assembled in Jan/Feb in Scotland for production testing before release to American Calan Inc.  We have some way to go to assure oursleves of high yield because of the Vp/Idss variations in the timing constant current JFET and the source/gate threshold voltage of the switching MOSFET.

As usual I have a supplimentary question.  We use the RI-INL-W9QM-30 since we need to install multiple groups of animals which can be swapped between pens. We thereore need multipe tags with the same ID.  Also we offer spare tags which can be programmed to replace any lost keys. We provide PC software to calculate our unique 64 bit payloads and additional crc chunks.  This is more complicated that necessary but arose in response to problems with 1(1,2,4,8 ---) bit payloads that interference and framing errs could resolve into a logged animal ID. We first increased the base numbers to over 1024, then added our Mfg chunk but adding the additional in 64bit CRC does not cost us anything butsecures what must be close to winning the lottery for $64M.  Gives us peace of mind.

We therefore chose the Write Tag. We could use the read only tag  if we could load in our code and then lock the memory of the tag. As I understand it we cannot do this - ist this the case ?.

Best regards and Happy New Year

Colin we might be in competition...where do you stand on the issue of IP?

We must be in parallel universes; amongst other things we are also developing "arrays of massive numbers" of "near-field" Readers for cattle feed-lots. Here the beasts are confined and feed regularly from a trough which is filled daily by a huge truck which decants "special grow fast food mixtures"...

Like your cows, they hear the truck coming , salivate and rush over in anticipation of lush feed and er...er..hormones...etc.

Our concept uses the existing HDX ear tags they arrive with (feed-lots are like a holiday resort for them)...next stop, er...er...the golden arches...

We are developing a plastic mould/embedded retro-fit "Feed-Trough Lip Reader"...as with you, about 600mm apart, and yes when they arrive
or are "inducted" ... they are skinny and 100 days later they are fat... consequently, how many bovine can dine side by side is a issue, but is
solvable.

Our strategy is to multiplex, and while there may be <100 beasts per pen and then >50 pens... so scanning 5000 readers (assuming our
client can afford such a thing) one at a time as in a massive multiplexer will take time...to speed things up we propose to interleave the
multiplexing say repeat it every 10 adjacent reader.

Unlike your task to open the feed door to a "qualified animal" (my understanding)...we will send the UniqueAnimalCode back to a remote
remote host...here it is time stamped and put into a form of ExcelSpreadSheet...several things are deduced from the "clever in the
spreadsheet"...how many minutes each beast had his/her head in the feed trough (food intake by inference) and if a beast is repeatedly
arriving "at the end" of the cue/trough then this is a sick cow (take him off to the house vet)...etc

Colin, we use the RFID EarTag as a pointer to a row/column in a spreadsheet, wherein can also reside each beasts total history, eye colour
and inside leg measurement if you so desire...it may be worth your while reflecting on this mechanism, and then sending back an "open door" command?

As I understand it, you have a "house-brick" sized box around each cow's neck...do they still retain an RFID Eartag or do you cut it out?

I am still a little unsure of your use of the term "co-existing" how do the untagged cows get to eat if they cannot open a door?

In America/Canada we had issues with "co-mingelling" of animals... where in the herd were a mixture of FDX and HDX Tags...here it was
necessary to have a reader that could read both...ISO allows for this but we have drawn a line in the sand..."it's over red-rover",
Australia has decided on HDX... the rest of the world is still playing dice!

Your use of "random" is creative ... we do some thing similar as part of our concept of "dynamic adaptation"...I think I might buy a ticket
in that lottery you are running.

Tarry a while yet, and we can future get down to the how's... but first the why's. You will agree the question is far more interesting than the answer?

Regards

Ray

Hi Ray,

Sounds as though we are in competition but I never like markets where there is no competition !

Regarding IP, out feed consumption logging relies uon individual  weighed feed buckets with no central computer management  and we never have un tagged animals in a pen - at least not intentionally.

We will be introducing gate activity monitoring  open instant and duration of feeding. I have the hardware at prototype level and it will be an Ethernet link over the 24v power lines.We also consider feed intake by inference a valid route round individual bucket weighing.

The eartag does not concern us since the neck tag - more like a tennis ball than a house brick does not compete because of the tombstone fence configuration which leads the

cow into position. If a feeder is not used for an unusual period, then we call in the vet or look for an inert heap under the snow and  prepare forsteak on the menu.

Yes we have watched the Australian uptake of HDX which we are just gaining practical experience with - so far all good except for the co-existence problemwhich we have now surmounted. In Europe the Mifar FDX is quite common but international parlour manufacturers seem to favour HDX.

One issue which you might have experienced is 134kHz amateur radio low frequency and industrial LF interference, submarine communications etc. Our readers can see close florescent light  PSU radiation but but so far this has always been far below problem level. So far we have not experienced problems but I am sure that we will in due course and may have to resort to electrostatic antenna screening to deal with EM waves. 

My use of "co-existence" is entirely focussed upon what our tags do to other manufacturer's products by placing our tags within their reader fields if they are HDX. Hence our Stealth approach where we make ourselves invisible to enemy radar. Within our own application ear tags are well out of the way during animal entry and it doed not matter after that since their payload will be rejected by our software. Since every animal has a unique feed position we are in the business of feeder recognition which we can then tie to the cow database.

Good to compare notes.

Regards,

Colin

Thanks Colin, I still cannot form the right mental picture of your set-up. Allow me to be your devil advocate.

Is it a metaphor for those french ducks they nail their feet to the floor and force feed them?

Is there only one cow in a pen? ... if so, what is the utility of RFID at all...a tripwire and microswitch or a foot switch would open the door as the beast approaches?... why have a door at all...count buckets?

You speak of identification certainty  in that like that Russian egg within an egg within an egg within.....etc you append extra digits to the animal's UID...is that all you do with the "write capability of the RFID Tag?... surely the standard RO Tags are adequate?

I put it to you that if the beast has an existing HDX ear-tag and now a HDX neck-tag and you only use a 20mS Charge field then BOTH tags will simultaneously emit their Telegrams/Payload...whereupon it is conceivable that a temporal Data collision will likely occur

You imply, the Ear-tag does not "compete" because of a tombstone fence? ...I put it to you that once the animal's head is up "real close" to your ferrite aerial, the Ear-tag may yet even have harvested enough to emit either a full or "PARTIAL" telegram...and they both proceed to speak (over the top of each other!)

The Reader now has two overlapping telegrams (one bit corruption is all it takes)...and now any CRC test will be failed for BOTH tags...yes/no?

So have you ever found that "sometimes" the door will not open even though the cow is banging its head against the RFID door...Remove the Ear tag and put it back in a couple of months time.

I can also see a case where this same "dual RFID" cow might not be seen by a second party conventional reader...if the "neck-tag" is still emitting its premature (or distorted) telegram just as the "ear-tag" is just starting...perhaps reduce your 20mS charge/kill time down to say 15mS?

it is clever that most times the stealth tag imparts invisibility to the readers of other's but what happens to that cow, has he made it to freedom and can runaway ...no one knows he is/was there?

Convince me it is life or death necessary to concoct an "Enigma" grade UID code (BlechlesyPark style)

Yes, Amatuer/Ham radio is just above 134.2Khz we don't expect too much problems, an "RF site survey" will find the culprit and give him a good talking to...I think in Europe (Germany) are some Weather/stations beacons that should be watched...he won't be hard to find, his gigantic aerial is a certain give-away!

We use electrostatic shielding (carbon spray) now to discharge hot weather electrostatic build up (ie minute discharge currents that might mask a vital passing tag etc...it is useful)...however it is no protection for "E/M Radio" waves or time varying magnetic fields...we have other solutions for these. Electric fences a a small issue and groud currents passing through floor concrete reinforcement are detectable issues.

Colin, could you again describe your installation?...I am a slow learner.

Regards

Ray

Hi Ray,

Our animals are loose housed in groups and each animal is given a feed position in the tombstone fence which it can only access becausre of its neck halter tag.

The range is only around 10-15cms so during the entry process, the ear tag is well out of the field. The animal raises its head to enter the fence so the neck tag reaches the door hot spot much earlier that the ear tag. Once the gate is unlocked, then yes, the ear tag can be energised but the animal by then has made its entry so any collision is irrelevant. The tombstone fence dimensions are critical as is an understanding of how cattle negotiate them.

Yes the extra payload CRC is more a psychological tool than of practical value. Is a comfort though to users who are not au fait with the technology. The extra security also ensures ear tag payloads cannot compromise entry. I am no Alan Turing so Bletchly Park will not be calling on me.

We have looked at conductive sprays but they apparently  have limited LF effect.  Copper foil seems to give better results as long as we avoid short circuit turns.

Best regards,

Colin

Thanks Colin

Now I see... I think I see...you have say three cows in a pen... cow"A" cow"B" and cow "C".... up one end of this pen are three FeedingStations  ,"A" "B' and "C".

Cow "A" can only access Feedstation "A" and so on....therefore each cow has its own special food-mixture...you have given each cow a "tennis-ball-key" ...you are experimenting on growth-rates for different compositions (buckets) of growfast/feelgood concoctions...am I getting closer now?

Concerning the "smoke and mirrors and appeal to authority" of a BIG/Bigger/biggest code.... I will let it go through to the keeper.

So, if it is possible for a data collision while his head is face-down busy eating, is it possible the gate will slam shut and well...well...another bump in the snow?

I find your problem intoxicating

Regards

Ray

Yes high resistance conductive carbon spray is only good for "draining off accumulated charge"...we should talk more on the low ohmic conductive foil and skin effect and depth of penetration of induced currents and incident and anti-phase flux and then on to "shielding"...

So, the TMS3750 can have a digitally selected carrier frequency....have you ever used this capability or known anyone of the 7 Billion souls on this planet who has?

Getting late here now Colin...I must away to rest...but first...

By mimicking the mechanism of your "supplementary" question I just left you with a thought for reflection...you could well be that 1 in 7 Billion person we seek....let me explain and join some dots...I see a way back to your StealthKey

Your "StealthKey" probably has many turns and perhaps an inductance 1-2 mH... it may/probably even be resonant to 134.2khz (getting into muddy waters now as coupled resonant circuits are appearing before me) ...my guess is you have arranged for mechanical positioning just before the verge of critical coupling... ie the on-set of double humping...you speak of a fibre spacer and suggest a bit of "fiddelling" then epoxy in juxtaposition.

You probably has some efficient rectification and then a monostable mechanism using a Fet to short circuit the StealthCoil...let me assume this is so for a while yet...

Now...when you short the StealthCoil you can reasonably expect two things...

First the energy in the "either" is consumed in the ohmic component of StealthCoil and therefore the adjacent/shadowed/shielded RFIDCoil is robbed of charging energy

and secondly the RFID Resonance frequency will SHIFT HIGHER for the duration of the Short circuiting...if it could transmit then it would transmit (remember these are free running plucking oscillators here) on say 139Khz or whatever...

Now comes you with your TMS3705 and you have "quickly retuned its clock" to listen up high (changed the divide factor)...there is time dilation of course (16 cycles of one then 16 cycles of 0) but the UID code is/may still be there....

it's just that you thought you "killed it" perhaps you did a bit of that and chased it higher up the RF spectrum...reach up and get it?

Lot of if's and but's...however its just a thought. A similar reflection also relates to the 13.5Mhz cards up close.

Yes, your Stealth process may have created invisibility in the frequency domain....another parallel universe....think on it may be useful.

I never thought I would get a chance to us "either" in a conversation....but there yo go.

Regards

Ray

Hi Ray (Again),

Paints a pretty picture !  The gate is held open by the bovine neck until it withdraws after stuffing itself.  I never thought of using hydraulics to send the animal into orbit. Once the cow is in, the reader has no further part to play. When the cow departs, the spring loaded door flap closes and that is that until the chosen beast returns.

It is fascinating watchin a pen od say 12 cows learning to find their own doors.  It is a very human experience. First the hash and bash merchants experiment up front whilst the academics just sit back and watch. Then they just calmly walk up to the unoccupied doors and use them.. We even see cases wher a group of animals gathers round a feeded and using not too much imagination they discuss what they are seeing and then get downn to business. But of course we have a long established training proceedure. The whole relies hugely upon experience and the ability of an animal to become confident when things work.  In the early days, the locking bolt was accessible to the mobile tongue and we had animals leaning over the fence and pushing the bolt back.  Wjen animals were fed in a locking feed frame there were instances where an animal had to be taken out of the herd because it flipped over the locking latch at the end of the fence and all the group gained free access.Herefords seemed particularly bright and when out on service trips I could not get at the works because of animals withing to find out what I was up to, Latterly at the tail end of my career I partnered an ENT surgeon when restoring opera singers to their career and my work with cattle added substantially to the psychology although as an opera singer myself and a sound studio engineer, I had a few more tricks up my sleeve.

I have great respect for the grey matter downstream from the ear tag. A t one farm show a group of us managing a cow barn made the mistake of visiting the beer tent. During our absence, the group pens got mixed and sorting them out in a state of liquid stupidity proved that our abilities had fallen below those of our charges. We came back the next day to sort them out.

When faced with technology there are times when this intelligence can be put to very good use ! Access to feed problems inuces the Ph.G  in most animals.

Clever cows....clever cows... those 12 cows, can you freeze dry them and shrink-wrap them with 12 typewriters and post them to me...I need help with firmware/software writing...perhaps send them by sea mail on the cardboard replica of Dartmoor prison...failing that you could consider issuing a cork and a whistle to each cow.

The cork in one nostril and the whistle in the other....as they approach their pitch will forewarn the feed-gate...(sesame)

Later I would like to discuss your GridDipSolution...curiously I see some practical value there...but not right now...I have no artistic merit/skill however my favourite Painter is Titan(1473-1576) and in particular his work ... "Noli Me Tangere)

Regards

Ray

Yes Ray,

I have been trying to work out your time zone !

As you accurately deduce it ia all a metter of LC and R.  I steered clear of pickup coil resonance to avoid the critical coupling issue and the bandwidth twin peak penalties. Also there is very little power that can be taken from the tag and yet I needed the advantager of resonance to harvest the Stealth key power.

My pickup coil is a 500 turn job solely selected on transformer recovery of the tag signal.   There was no power available for logic and so the harvested voltage is simply used to charge up a capacitor 33nf in 38mS . Somewhere I worked this out at under 1uA  but the coil is also damped by a 1Meg load.  I can probably increase this to about 2Meg but I dislike unloaded inductances especially when feeding a rectifier. 

Yes once the short is on, the tag coil will be affected but in practice there is enough charge to sustains the short well beyond the payload transmission.  I will be exploring this is measurement detail during the pre=production prototype run.  The fact is that it works and kills the transmission phase.  I expected the short to prevent the short on time to be sustained long enough but on the scope the Stealth Pickup coil does not collapse significantly and I am not sure why not.  I will diagnose this during the pre-production run but at these extremely low signal powers I cannot even trust my scope.

So the signal path is pickup coil, single diode detector small rervoirr cao and a zener limiter at 3.7v.  The DC then feeds a constant current JFET which charges up the 33nF timing cap through a resistor trimpot adjusted over a 2Meg range.  This is the nastly bit of the circuit since it accepts a ridiculously high variable JFET and output MOSFET dynamic behaviour.  The rise time of the 50mS is also used to drive a 33nf Cap dischare transistor to ensure the 38mS timingalways starts from the same near 0v level.

The ioo% need was to minimise Stealth power consumption to avoid affecting the tag operation and whilst this has not been avaoioded, the apparent loss in sensitivity is very small and acceptable in our application.    These are the determining criteria the Stealth Key does not damage our application and it competely blocks payload transmission in a longer charge cycle=>50mS.

There is a great deal of formal analysis work to be done and empirical selection of the nylon spacer has still a bit to run since this determines the hiatus zone as the stealth key enters the field and the power drawn from the tag inlay. The fact is there are dairy cows successfully passing through a Dairy Master HDX ID Parlour and it solves this problem where our neck tags collided with the ear tag payload.

Your comments are very helpful since their ain't many people to compare notes with in this matter.  I am most grateful.

Our legacy "grid Dip"  simply used  frequency channels from 30kHz to 115kHz. The challenge here was feedlot teperature swings and we designed a feedback system which secured reliable oscillation unless the approaching key introduced a dynamic variation,  It has worked well for half a century and there is a least one research institute who is still using equipment which I built in 1970 in Scotland.  In the early days we did have our share of disasters but the learning curve was travelled.

Best regards,

Colin

Hi Klaus,

I still have some concerns about the supply of the RI-INL-W9QM-30 inlay  since the departure of the W9QL disc has been difficult to understand.

Our application takes advantage of the write facility to enable duplicate pens serve more than one group and spares mangement is also eased by simply being able to replace lost keys by programming to order.

We could perhaps use RO tags if the initial payload could be put in and locked by our own technicians.

So the two question are :

1) Is the RI-INL-W9QM-30 safe to use ?

2) Is it possible for use as OEMs to load the payload into read only tags and then lock ?

Very Many thanks,

Colin

Colin...I share this with you...there are multiple Readers inside this ...will talk about it when I return from Bush....the dog is in fact an Irish Wolf hound...

Regards

Ray

..."Hiatus zone"... forty three years earlier Adolph offered a pole star of "social invariance", then
comes you with "enforced variance" ...to announce with a warble the presence off a passing
sprite...and now Pilgrim, after another fourty three years, travelling down a twisting loci of
heuristic learning, you arrive here and now...the veil which partitions the analogue from the binary
is not an armband for lament...that line in the sand is not an aggressive warning but rather a new
starting scratch for old dogs...well done sir;  It won't be long now until every pea and every carrot
and every...every...thing, has a dust-mite sized RFID tag...I leave it to you to draw the curtain on
our sorjourn...I fear others may find this dialogue sadly tedius... My fear is that the "early
others" who can/would speak on the why, not so much the how...have left this mortal coil...
My comfort in this forum is reinforced when Josh Wyatt, in a line of code spots an error , a
transposition errror, of 0x26 for 0x01
Untill later then.

Regards Ray

Hi Colin,

the TMS3705 will NOT be stopped, we rather released revision B, this is the reason why the TMS3705A1DRG4 shows NRND! Revision B TMS3705BDRG4 shows ACTIVE and is now set up for free samples! http://www.ti.com/product/tms3705

Regarding the RI-TRP-W9QL-30: We are working on a solution here, but we can't offer yet a replacement but will keep you posted!

Best regards,

KSA

Hi Ray,

I enjoy you philosophical bent !  Anyway enjoy a good 2013 and take care not to fall off the fiscal cliff.

The concept of mutiplexing RFID antenna is interesting with the time consu,med by the charge phase and added problem. My thoughts would be to ripple out phase delayed power phases so that the sequential responses flowed perhaps 2-5mS appart to shorten the scan.  There could be many more options to what is effectively a sequential search for data.

Rises many intriguing challenges..

Enjoy a productive 2013.

Best regards,

Colin