I have a 3 com 3c892a modem. If I set it up to "Use one B channel" everything is fine. If I set it to "Use two B channels" everything is fine. But if I select "Add second B channel as required" the second B channel never picks up. I have a backup 3 com modem and it works the same way. I have call waiting on both lines and if I'm on a voice call and get a second call the phone beeps so I can pickup the second call. AT&T has checked the lines and does not find anything wrong. I use one of the lines as my land line so now I'm limited to 1 channel most of the time. I don't know if it's a modem problem, a telco problem, or it's my ISP. If anyone can point me in the correct direction to fixing this problem. I would appreciate it.