Telecheck is a processing and approval service used more by merchants than banks. It either tells the merchant that the check is OK to accept or can run it through as an electronic debit and return the check to you. I believe that their database merely keeps track of whether you have a history of NSF and is not able to access current account balances with your bank. I'm pretty sure that they probably also have a history of your prior transactions cleared through them so if you normally write checks for less than $100 it would be unusual for you to be presenting a check for four figures.
