[*] PRI lines

[Sean Walberg]

The D channel runs a protocol called ISDN Q.931 that lets both ends tell
each other what's going on, ie "Hey, slot 6 is ringing, callerid is
xxxx, etc".  The B channels run only voice.

Since the other 23 channels are using the full 8 bits per T1 frame there
is no room for the signaling within the voice slots, as with a regular
robbed-bit T1 (where you get 24 voice channels, but only 56kbit per
channel)

The PRI method is out of band signaling, the robbed bit is in band
signaling.  You'll also hear them referred to as common channel
signaling and channel associated signaling respectively.

Sean

On Tue, 2005-12-06 at 10:02 -0600, Dominic Crompton wrote:
> I am a little confused about PRIs. A standard PRI T1 line has 23 B channels and one D. What is the D channel used for? I realize its for signaling and control, but what does that mean exactly?
> 
> incase your interested find pricing below for two way
> ISDN PRI's out of the GT colo (1 Wesley)
> 
> 1 Year
> Monthly: $650
> Installation:$500
> 
> 2 Year
> Monthly: $618
> Installation:$500
> 
> 3 Year
> Monthly: $585
> Installation:$500
> 
> 
> 
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