AT&T sending three or four digits

[coniglio]

whenever I install a new T1, AT&T always asks me whether i want them to send three digits or four digits. How do i make this determination? They keep telling me it's based on "what the PBX wants". Where do i find this info when I am in the PBX? what load? thank you for your help.

 

[phonejack99]

Normally the answer would depend on the length of your extensions i.e, if you use 3 digit extensions have ATT send 3 if you use 4 digints have ATT send 4.

 

[coniglio]

so it's that simple, huh? well, let's say I use three digits and for whatever reason we decide to go to 4 digit dialing. (A) is it as simple as just adding an extra digit to everyone's ext and (B) would i then contact AT&T and ask them to send FOUR digits, as they are currently sending THREE for this particular T1, and by the way that office does use 3digit exts. thank you.

 

[phonejack99]

In essence that is correct. You will also need to change your LDN0 in your CDB, this tells the PBX how many digits to translate a DID call into an extension.

 

[coniglio]

so if I were installing a brand-new T1 circuit, should I be looking at the LDN0 in my CDB first? or is that just if I am changing the numbering plan? or do i have AT&T send the same digits as my exts and THEN do the LDN0? in other words, is that parameter already set regardless of whether I have at T1 or not?

 

[coniglio]

OOPS, ONe more thing, phonejack 99. In my NYC PBX the LDN0 is set to 2070!! based on waht you just wrote, i would have thought the digit "4" would be there, as our exts are 4 digits. what is the significance of 2070?? that ext means nothing to me.

 

[phonejack99]

The LDN0 -- Listed Directory number entry 0 -- is used for a few different things. For purposes of answering this question the 2070 telss the PBX to use the last 4 digits of a did call for routing i.e, 123-456-7890 would be translated to ext. 7890.

Again, generally the easiest way to do the T1 is to get the carrier to send same amount of digits (DNIS) as the digits length of extensions.

 

[coniglio]

thank you, but i still don't understand the significance of 2070. It is not the last four digits of our telephone number. It seems to just be a made-up, unused DN. so could it have been any four digit #?

 

[acewarlock]

If someone dials 2070 it will go to the ATT.

At my location we use 7 digit dialing the LDN is 6395008 our DID range is 6395000 to 6399999, the 7 digits of 6395008 tell the co to send 7 digits, if someone calls 6395008 the call goes to the Attendent. the LDN can be any number.