Do I really need to dial "1" when calling a domestic US phone number?

[onepolarbear]

I have been using Google Voice on my Obi110 for several days now.

When calling domestic US phone numbers, I simply dial the 10-digit
number and the calls go through.  (example: 212-555-1212)  Haven't
had a domestic US call that didn't connect yet. 

I read somewhere that I should dial it as 1-121-555-1212.  How
important is it to dial "1" first?

Thanks!

[infin8loop]

The DigitMap on your OBi for the ITSP provider handling Google Voice is probably prepending a "1" to dialed 10-digit numbers. The DigitMap probably includes something that looks like "|<1>[2-9]xxxxxxxxx|".  This translates to "prepend a '1' to 10-digit numbers that start with 2 thru 9" (an area code cannot start with a "1").  Look in your Obi Call History and you'll most likely see that a "1" is being added for you to your outbound Google Voice calls that are dialed as 10-digits.  In the VOIP world the leading "1" for the country code is usually required as far as I know.  

[Lavarock7]

The remapping of numbers is what makes today's technology great. In the past a company might have had to dial 9 to get an outside line, 8 to get a company internal link to another office and so on. With remapping and knowledge of low cost routing, we can now force certain calls out through different paths and different providers all transparently.

Some people are remapping "911" to a 10 digit local number. and so on.