Simplify the following text for a Grade 10 native English-speaking person.
Original: For instance , the North American public switched telephone network ( PSTN ) uses a 10-digit dial plan that includes a 3-digit area code and a 7-digit telephone number .
Simplified: For instance , the North American public switched telephone network ( PSTN ) uses a phone numbers with a 3-digit area code and a 7-digit telephone number .