How does bank ACH work?

[manlymatt83]

So every night, does every bank get sent a spreadsheet or something with the transactions they need to run against their database?

I mean, how for REAL does this work. I understand logically, but technically?

 

[George P Burdell]

They just send the numbers over to each other over secure fax.

 

[RossMAN]

http://ilovechecks.com/ach/howitworks.html

 

[akshatp]

Each bank's president asks his/her Dr. if they are dying, then when the Dr. tells them they are being paranoid he hands them the daily list of ACH transactions.