All the articles I've read about it indicated that the rings were
standard.  A google search shows that typically the second number is two
short rings.  Further numbers may or may not follow a standard.  Look
here for some timing information on a few different signal spacings:
http://www.interconnection.bellsouth.com/products/lec/ringmast.html

Here you can see a similar list of patterns with timing information:
http://www.marko.net/asterisk/archives/0205/0157.html

I suspect you will find that there are 5 common distinctive rings, but
the order in which the phone company implements them may be arbitrary.
I also suspect that even within a given phone company it's not standard
due to the following case:
Customer sets up three numbers on one line.  Customer drops the middle
number.  I don't have experience in this, but I hope the phone company
keeps the current signalling as is.

If you provide support for all ring types, then simply pick an order
that appears to be common and allow customers to customize it if they
want to.  Or better yet put the device into 'program mode' and call each
number one at a time in order.

-Adam

Shawn Yates wrote:

><reposted due to malformed subject line>
>
>Can anyone give me a lead on where to find info on distinctive ring from
>phone companies?  Is it a standard across the US?
>
>Thanks
>
>Shawn
>
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