In Cisco CallManager 4.x connected through E1 to 3845 router, which is used as a gateway, when an IP Phone calls up a phone behind the Nortel PBX, the IP Phone gets silence for a brief period and then a busy tone

[TCC_2]

Core Issue

In this scenario, this can possible be an intermittent problem, that when a call generated from an IP phone to Nortel phone does not give any tone such as a Ring Back or Engage. The IP Phone receives just silence for some time and then a fast busy.

This can possible be a visio for this kind of network:

IP Phone--> CallManager----> E1 R2 Gateway(3800 Series)--> Nortel PBX--> Phone

Resolution

It has been observed that when Line signaling is defined as R2-Digital or R2-Pulse, the requirement for R2-Analog results in the same behavior.  In order to resolve this issue, change the Line signaling to R2-Analog.

Refer to these documents for more information about E1 R2 Signaling:

• E1 R2 Signaling Theory
  
     
• E1 R2 Signaling Configuration and Troubleshooting

• Country Options Configuration for E1R2 Signaling