ISDN engaged tone

[mtbuk]

Yesterday I experienced a problem with our ISDN 30. I could make calls using direct dial numbers to our internal extension numbers (ie from the outside world inwards) however from an internal phone whenever i tried to dial the outside world i would get a busy tone. I know very little about ISDN and was wondering whether it is possible for an ISDN line to fail in one direction only... in this case when we tried to call out.
I ask the question as last night this was the case however on testing this morning the issue has resolverd itself. We are using VOIP and no configuration changes were made on the router or through call manager which points me towards the ISDN 30.
Any help would be appreciated, thanks.

 

[jgideon]

Yes, this can happen. There are 'setup' messages that are 'intelligent' that are communicated between the switches for every call. If something isn't 'right' on either end at that particular moment, a call will fail.

 

[artesian2000]

I would work with the carrier to verify your d channel protocol. Sounds funky. I doubt this is a line issues being that the condition is only on outbound calls.