Extract digits from extension

[sn4p]

I'm trying to create a dialplan in extensions.conf that can accept a number like:

(123) 456-789

and replace it with 123456789 (just the digits) to use in the dial function to the SIP provider.

I'm having no luck using the REPLACE funcion. Any help appreciated.

[david55]

${FILTER(...)}

[Lexus45]

// Excuse me. Fixed.
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