[Asterisk-Dev] Question about E1 Card / ISDN PRI

Leo Ann Boon leo at innovax.com.sg
Fri Mar 21 18:12:20 MST 2003

Some answers:
1. ISDN PRI is usually from your telco to you. It's normally used to 
replace analog lines. 1 E1 PRI is equivalent to 30 analog lines, so you 
can imagine the savings in wiring. But, you can't directly plug a phone 
to an E1 PRI, it has to be splitted up using a PBX (like the *).

2. You'll have to use CCS (Common Channel Signaling) or more commonly 
known as D-Channel signaling. Excerpts from my zaptel.conf for an E100P:

The dchan is a must for PRI, it tells the E100P to use channel 16 for 
signaling instead of voice. The crc4 option is usually required for E1 
PRI, but if check with your telco. I've seen some E1 PRIs supplied 
without crc4 (no thanks to DMS100).

3. I don't think S/T or U applies to PRI, it's for BRI. Perhaps someone 
else can explain this better.

4. R2MF is an E1 CAS (Channel Associated Signaling), it's like T1 
robbed-bit signaling. PRI is CCS.  IIRC, the zaptel supports R2 
signaling for China.

Help this helps.

Vinod Sankar wrote:

>I have a few basic questions. Apologies in advance if this is
>the wrong forum for what should be a Digium FAQ.
>I'm trying to use the Digium E1 card to provide an IP PBX like 
>application to an enterprise that needs about 30 telephone lines, 
>in India. India supports R2MF and ISDN PRI (Euro ISDN) signaling
>standards. The Digium card supports only ISDN PRI. 
>The questions are, 
>	- Are ISDN PRI lines used only for branch to branch 
>(closed group) calling, where the PSTN is unaware of how the 
>channels are used (Voice/Data) or can PSTN switches terminate 
>voice calls from public analog phones into this ISDN PRI circuit ?
>	- The Zaptel configuration mentions framing options for defining
>spans for E1 lines as either CCS or CAS. Do I specify CCS for an
>E1 ISDN PRI line from PSTN terminating on this card ?
>	- What interface does Digium E1 card support S/T or U ?
>Also, quickly, what is the difference between R2MF and ISDN PRI ?
>If someone could point me to a website that has more info on these
>subjects, that would be great.
>Vinod Sankar
>Asterisk-Dev mailing list
>Asterisk-Dev at lists.digium.com

More information about the asterisk-dev mailing list