Hi, I am facing an issue with interfacing 2 older model PBXs in locations A&B with 2 newer model PBXs in location C&D. The PBXs have been connected via 2Mbps E1 lines. The problem is that I am not able to establish communication in tone mode dialling between the old & new PBXs while I am able to establish connection between all PBXs in pulse mode. The set of old PBXs & the set of new PBXs are able communicate with one another in tone mode though. Is this a compatibility issue that the PBXs are not compatible in only tone mode dialling? I would really like to know where the problem might be. Thanks Ishin