[Asterisk-Users] Difference between E1 and PRI

[Peter Svensson]

On Wed, 23 Feb 2005, Scott Stingel wrote:

> Good writeup!   Question regarding Q.SIG:  Can it be used to solve the 
> problem of signaling a remote switch to "take a call back" and extend it 
> to another channel instead?   This, as you know, is always a challenge 
> when using IVR in a call centre environment, when one wants to extend an 
> IVR call to a live operator without holding up channels in the IVR.

That problem goes by many names: tromboning, hairpinning, etc. There are 
several signalling methods, depending on what protocol is spoken by the 
remote switch:

 * q.sig has (can have) support for this
 * Explicit Call Transfer (ECT), used on EuroISDN I think)
 * 2B Channel Transfer, on 5ESS switches

I don't think these are signalled the same way. 

Peter