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You can use the "Input Mask" of the textbox field
You can specify the number of character as well as the input type.
Hope this help. Inform us if you need more assistance.
Did you literally mean at least 10 digits or exactly 10?
at least 10 digits
Thank you for your response.
Then please follow Jonathan's advice and use the placeholder characters for your input mask, to a combination of exacly ten characters.
Most phone number formats are as follows: 000-000-0000
So the mask would be something like ###-###-####
Does this help? Please let us know.