there's more to it than that - lots of phone/phone systems have built algorithms tell them how long a phone number is, and place a call once you've hit that length - for example "911" has a length - one thing that's been happening behind the scenes (mandated by the FCC) is that all the phones in the US have been quietly getting software upgrades to make "988" terminate at 3 digits .... this effectively means you can't dial local numbers that start with 988 .... there are no 7-digit numbers that start with 911 but some that start with 988 - there are no area codes that start with either.
It's all a tremendous ongoing hack ....
Interestingly it used to be that all area codes (and emergency numbers) had a 1 or a 0 as the second digit and no local exchange numbers did - that's why you didn't have to type that initial 1 (which is also the NA international dialing code) - exchanges could easily detect an out of area code call (and figure out the 7/10 digit thing). Then faxes and modems came along the number of required phone numbers in the US effectively doubled and they ran out
It's all a tremendous ongoing hack ....
Interestingly it used to be that all area codes (and emergency numbers) had a 1 or a 0 as the second digit and no local exchange numbers did - that's why you didn't have to type that initial 1 (which is also the NA international dialing code) - exchanges could easily detect an out of area code call (and figure out the 7/10 digit thing). Then faxes and modems came along the number of required phone numbers in the US effectively doubled and they ran out