The Textbox Delayed Callback extends TextBoxes by doing a callback when the DelayTime has expired after user input. It has been used in web applications doing the callback after the typing has stopped, with the devices: Check Reader, Credit Card Number Reader and a Barcode Reader. It can also be used to make the callback after the user has finished typing.
The Textbox Background Callback extends TextBoxes by doing a callback in the background so the user typing isn't interrupted. It has been used in web applications with a GridView, the callback filters the data shown but the user typing isn´t interrupted in any moment.