[asterisk-dev] flash transfer problem in asterisk integration with old PBX

[Andrea Giuliani]

I've tried to transfer a call using the Flash command, but with my
configuration it doesn't work.
I have a traditional PBX connected with a zap channel to Asterisk that acts
like an IVR:

TELCO line --> traditional PBX (FXS) --> (FXO) Asterisk

>From the TELCO line I can make a call to the traditional PBX and reach
Asterisk, the IVR system on Asterisk answers the call and I can dial an
extension (for example 42 that is on the traditional PBX). In the asterisk
dialplan I've set to transfer the call using Flash() like in this example:

exten => 42,1,Flash()			
exten => 42,2,Background(silence/1) 	wait 1 second for the traditional
PBX
exten => 42,3,SendDTMF(42,250)
exten => 42,4,Background(silence/1)	wait 1 second for the traditional
PBX	
exten => 42,5,Hangup()			

When I dial the extension 42, the phone 42 on the traditional PBX rings but
when I answer there isn't communication with the call from the TELCO line
and after a few seconds the line hangup.
Here you can see what happen in asterisk CLI console:

       Executing Answer("Zap/4-1", "") in new stack
    -- Executing BackGround("Zap/4-1", "a_suoni_plink/menu_esterno2") in new
stack
    -- Playing 'a_suoni_plink/menu_esterno2' (language 'it')
  == CDR updated on Zap/4-1
    -- Executing Flash("Zap/4-1", "") in new stack
    -- Flashed channel Zap/4-1
    -- Executing BackGround("Zap/4-1", "silence/1") in new stack
    -- Playing 'silence/1' (language 'it')
    -- Executing SendDTMF("Zap/4-1", "42") in new stack
    -- Executing BackGround("Zap/4-1", "silence/1") in new stack
    -- Playing 'silence/1' (language 'it')
    -- Executing Hangup("Zap/4-1", "") in new stack
  == Spawn extension (incoming, 42, 5) exited non-zero on 'Zap/4-1'
    -- Hungup 'Zap/4-1'

I've tried the following changes to the dialplan in my example but transfer
still doesn't work:

- I've tried to use wait(1) instead of Background(silence/1)

- I've tried without Background(silence/1) or  wait(1):

exten => 42,1,Flash()			
exten => 42,2,SendDTMF(42,250)
exten => 42,3,Hangup()			

- I've tried without the Hangup() instructions at the end


Has anyone the same problem like me and any suggestions?