asterisk users - Sep 2005 - Asterisk vertical service activation codes

Anybody know anything about using "Asterisk vertical service
activation codes" as described in the wiki:

http://www.voip-info.org/tiki-index.php?page=Asterisk+vertical+service+activation+codes

Specifically I'm interested in *0 that (apparently) flashes an
external trunk on bridged channel.  Nothing seems to happen when I use
it though.  Do I need to do something special in extensions.conf or
perhaps features.conf to get this to work?

Thanks,
Hugh

Here's what I learned (thanks Larry):

For example, assume you're paying for three way calling from your
telco, and you want to place a three way call.  First establish a call
with person A.  Press the Flash (or Link) button.  When you get the
dialtone from Asterisk, press *0 and Asterisk sends the flashhook to
the CO.  Now you hear another dialtone, this time from the CO.  Now
dial the number for person B.  Press Flash (or link again), then press
*0 to flash the CO again.  Now you have established a three way call
through the telco.  This only works with Zap channels of course.


Hugh