Alex,
You will need the following commands on the CME connected to the PSTN.
voice service voip
allow-connections h323 to h323
If you want to forward and/or transfer calls from the second CME to the first or out the PSTN connected to the first, you will need these commands on the second CME.
telephony-service
call-forward pattern .T
transfer-system full-consult
transfer-pattern .T
These commands allow transfer and forwards to all numbers. You could also restrict these functions by replacing .T with 3... for example to restrict transfers and forwards to extensions 3000 to 3999.
Hope this helps. If so, please rate the post.
Brandon