How ATMs work

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How ATMs work

Postby cibo_spazzatura » Wed Aug 27, 2008 3:16 am

Hi everyone!
I have a trivial question about how ATMs work, in particular; how does the ATM work in relationship to updating the withdrawer's account balance?
i.e. When someone withdraws the money, is his/her bank account immediately updated (real-time), or are these transactions being stored in the ATM Controller which then runs a batch process to update the respective bank's accounts?

Take the following scenario:
Say I have $1,000 withdrawal limit but I only have $600 in my current account.
If I withdraw $300 from it, will the ATM update that current account straight away (real-time), or will it log this transaction and run a batch process at a certain point in time to update my current account?
What I would like to know is that, if the later is the case (i.e. a batch process is in place), will the system allow me to withdraw $300 two more times, (hence exceeding my account balance by $300) since I haven't gone over my daily $1,000 limit?

Many thanks in advance!

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Postby fffresh » Thu Aug 28, 2008 2:28 am

They're always in real time. Even those rinky dink ATMs you see inside laundrymats and sketchy stores have a phone line hooked up to them that connects to check your balance. When you overdraw it's not because the ATM wasn't told you didn't have enough money. Banks seem to let people overdraw a little now so they can hit them up with hefty fees.

Answer- fraud excluded it's impossible to fool the ATMs since each transactions is verified with the bank before it's processed.

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Postby Mogul of Pineapples » Thu Aug 28, 2008 3:08 am

Yeah they have to check the card otherwise the machine wouldn't even know if it's a valid debit card or not.

I'm waiting for the day when the ATM gives me one less $20 bill than it's supposed to. Anyone hear of that happening? I wonder how you would deal with that.
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Postby magyar1045 » Thu Aug 28, 2008 10:45 am

A few years ago I withdrew $60 from my bank's ATM, but when I went inside the branch to break up one of the twenties into fives, I was told that that $20 bill was counterfit. When I told them that that $20 bill came out of their ATM, they immediately closed down all of their machines. Ultimately they discovered that every 50th $20 bill was counterfit. Of my original three $20 bills one of them was the 50th.

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Postby AnthonyBarone » Thu Aug 28, 2008 4:33 pm

These folks every find out why that ATM was rigged with counterfeits? Sounds like an inside job to me if the bank ATM had a fake every 50 bills.

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Postby Cucumber » Thu Aug 28, 2008 11:12 pm

What bank was this? Was it only that atm that had the fakes or was it every atm from that bank?

THAT IS CRAZY! you would think a bank would be the last place you'd find counterfeit money!
Stop talking crap about him!

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