[asterisk-users] PRI vs "Digital Trunk"

[Michael Collins]

> Hi, can someone enlighten me as to the difference between a PRI and a
> "Digital Trunk" (other than cost)?

Barry,

A "digital trunk" from the telco is most likely as you said - 24
channels of 64k voice.  (I know, technically it's "data" but the "data"
is just digitized voice.)  Think of the digital trunk as the equivalent
of 24 analog phone lines.  They can all be in hunt, some in hunt or
none.  (Depends on the carrier and your specific needs.) They can be
inbound, outbound or both.  (Again, depends on your needs.)  On the
digital trunk, the signaling is all done on the individual channels - if
a call comes in on channel 7 then channel 7 will see a signal from the
telco - frequently this is a "wink" signal.

A PRI is, again as you said, 23 voice channel with one data/signaling
channels, unless you're outside the USA in which case it's 30 and two.
All of the call setup, tear down, etc. info is sent on the D channel(s).
Since the D channel is actual data, and not just touch tones and hook
flashes, the PRI can actually do more.  For example, you can customize
the caller ID info that is sent out, whereas on your digital trunk the
carrier will control what caller ID is sent to the called party.  If you
want some more detailed info on ISDN (both PRI and BRI) then check this
out:
http://www.ralphb.net/ISDN/intro.html

I'm surprised that your carrier is charging more for a PRI.  Here in
California my carriers are dying to sell me PRI's instead of digital
trunks because they feel PRI's are easier to maintain.  (I don't know if
that's true, but I've had more than one carrier tell me that.)

Who is your carrier and where are you located?

-MC