DAHDI (previously Zaptel, also/originally Zapata Telephony technology) is/was the
hardware/software/systems implementation that allows Asterisk to interface with
physical telephony interfaces, provide functionality in software essential to traditional
telephony (whereas previous, hardware-implemented designs did this in rather expensive
hardware), and, probably most-important to the “radio” type uses of Asterisk, provides
synchronization, routing, and combining (conferencing) of audio streams within the system.
So, it is essentially an interface between the “physical” “telecom” world, and the “computer” world.
Asterisk is the “computer world” part of the system. It provides “call-level” telecom functionality
(call switching, call routing, voice interaction, application interface, logging, etc), in addition to
audio-stream-level interface and functionality for computer-related voice transport (such as VOIP).
Since Asterisk has good application support, it was easy to make it a REALLY good platform on which
to implement radio control, since it had nearly all of the characteristics necessary to do so inherently,
and was not difficult to add what it lacked.
LibPRI is a protocol library for for Primary rate ISDN telecom services. It was included mainly for
completeness. I seriously doubt that anyone that initially implemented a radio system has much use
for this, but trust me, several people that initially implemented telephone switches using my distro
and
THEN decided to put a radio interface or two on it, were certainly happy I did it this way. Obviously, LibPRI is not needed for a purely “radio” environment.
Zaptel (as mentioned above) was the previous name of DAHDI (don’t blame me!! I didnt come
up with EITHER of these names!!)
Jim WB6NIL
“Daddy of DAHDI” – As I was called by Mark Spencer circa 2008 (while at an Astricon)
P.S. I cant tell all of you how tempted I was to answer more like this:
DAHDI - Counterpart of the “MAHMI” technology. Once together, DAHDI and MAHMI spawned
a
number of derivative technologies, such as “SONNI”. Sadly, DAHDI and MAHMI don’t functionally inter-operate well anymore, and, as you might imagine, SONNI, now requiring two distinct interfaces (one for DAHDI, one for MAHMI), sometimes has interface “issues”. 
···
From: kk6ecm@gmail.com
To: App_rpt-users@ohnosec.org
Date: Thu, 11 Sep 2014 19:51:41 -0700
Subject: Re: [App_rpt-users] What is Dahdi?
This is what I understand… but looking
for an expert view from someone else.
Dahdi -
Asterisk & hardware device interface
Asterisk -
telephony switching and PBX service
Libpri - protocols
used by Asterisk/Dahdi?
Zaptel - interface
functionally similar to, and predating Dahdi?
Bob
kk6ecm
From:
app_rpt-users-bounces@ohnosec.org [mailto:app_rpt-users-bounces@ohnosec.org] On Behalf Of George Csahanin
Sent: Thursday, September 11, 2014
6:53 PM
To: App_rpt-users@ohnosec.org
Subject: [App_rpt-users] What is
Dahdi?
OK, not being a
wise-ass, not trying to be stupid, that part’s covered. Just trying to
understand.
What are the specific
functions of:
Dahdi -
Asterisk & hardware device interface
Asterisk -
telephony switching and PBX service
Libpri - protocols
used by Asterisk/Dahdi?
Zaptel - interface
functionally similar to, and predating Dahdi?
I know they are all
part of the whole package, and that whole package still has me in awe. But
being very curious type I wanted to know how this all comes together.
In my simple mind I
axe: why isn’t Asterisk enough? I know what that one is, but as I use
app_rpt daily I wish I knew which of the above are providing what part of the
overall system.
George J Csahanin
W2DB
Allstar 2360 Echolink-Free
Cedar Park, TX
512-401-2630
home
401-338-0568 cel
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