[Asterisk-Users] E1 legacy multi PBX integration?

[magnus]

Hi, I have an asterisk server with a quad E1 card, Span 1 to PSTN, and calls
flowing fine to and from the PSTN. 

I would now like to connect a legacy PBX to span 2 of the E1 card, I made a
crossover, configured zapta.conf and zaptel.conf.
 
Zttools shows both spans as up and active, but I am now stuck on how to 
a) Make calls out from legacy PBX to pstn and 
b) how to receive calls from the PSTN E1 bridged via span 1 onto span 2 and
into the legacy pbx. 
c) let the two switches extensions calls each other. 

I have reviewed the WiKi and the documents cover the x-over cable & the
settings for the legacy pbx, but not the steps (config) needed in I guess
extensions.conf 

- If someone could share experience and a sample configuration to achieve
this, I would be grateful. Fyi from the 100 or so ddi's on the PSTN E1 I
would like to share 50/50 between the switches. Do all 100 ddi's have to be
present in both extensions.conf?
Regards
Magnus