[asterisk-users] Transfers on an inter-PBX PRI link

[Vieri]

Hi,

I am trying to understand why some of my call transfers fail.

My scenario is as follows:

Legacy PBX1 ---PRI (EuroISDN) Zaptel--- Asterisk PBX2

Step1: PBX1 extension 101 calls PBX2 extension 102

Step2: PBX2 extension 102 answers the call and transfers it to PBX1 extension 103

Step3: PBX1 extension 103 answers the call and transfers it to PBX2 extension 104

Step3 fails and extension 103 is reconnected to 101.

Why is Step3 failing and how could I change my setup so the transfer succeeds?

As a side question, I'd like to know if I could "free" the "unnecessary" zap channels created in Steps 1 and 2.
On analog channels I could SendDTMF(${EXTEN}). I don't know how to do that on a digital pri line and if it requires that the legacy PBX be compatible.

Anyway, I'm not too worried about freeing the PRI channels. I just want "Step3" to work.

Is it possible, "somehow"?

Thanks in advance,

Vieri