Flashing An outgoing or incoming connection is being established on the specified B-channel. There is a successful connection on the specified B channel. D LED Off The ISDN D-channel is not currently active. This can be a normal 'idle' state on some networks and PBXs, but the D channel should be quickly activated if you try to make a call. Flashing The ISDN physical interface is activated and initializing.
Continuous flashing indicates an error in the initialization process.
No data transmission is possible. In the case of continuous flashing, AT status commands can be used to identify the problem. The ISDN physical interface is not synchronized, or is improperly connected. This can be a normal 'idle' state on some networks and PBXs, but the link should quickly synchronize if you try to make a call. The ISDN physical interface is synchronizing.