Obi110 keeping line open on PBX

[Gavo]

Hello,

I have two OBI110 in series with lines 1 & 2 of an analogue pbx. All is working fine apart from the lines being held open for around 5 minutes (may be exaggerating) after an outgoing or incoming call has finished.

Any ideas ? It's a UK pbx  (BT Versatility) so 600ohm.

Cheers

Gavin

[hwittenb]

It sounds like the OBi is disconnecting the PSTN Line port based on an extended period of silence instead of detecting a disconnect signal such as a CPC (momentary loss of voltage) signal, a disconnect tone, or a polarity reversal issued by your PBX.

I would try to determine if that is in fact the case and if the PBX is issuing any analog signal on the line to signal disconnection and if so why the OBi is not detecting it.  The signal goes by different names in different parts of the world.  Calling Party Control or CPC, Disconnect Tone, Disconnect Clear Time, Disconnect Supervision, Open Loop Detection are some of the terms used in conjunction with the signal.

The OBi has a number of parameters you can work with under Physical Interfaces-->LINE Port-->PSTN Disconnect Detection. 

[ianobi]

Gavo,

I don't have a BT Versatility to test this, but a know problem seems to be with this PSTN setting:

Program > System Programming > Lines > PSTN Programming > Guarded Clear.

Setting it to "unguarded", or whatever the alternative setting is, may help.

[Gavo]

It was exactly that. Thanks ianobi.

Switched off guarded clear on both incoming line ports on the pbx and all is working just great.

Cheers
Gavin

[guyjarvis]

I'm experiencing the same problem in a shared office where I have no access to the pbx and the landlords are totally unhelpful. Is there something I could do with the obi110 settings?

[ianobi]

I think hwittenb has it pretty well covered in Reply #1.

The OBi defaults should work fine if you are in North America. CPCTimeThreshold varies in different countries. For example, in the UK you would need to set it to something like 100. Also different countries use different DisconnectTonePattern. It depends what your PBX is putting out as a disconnect signal.

[guyjarvis]

I think editting CPCTimeThreshold to 90 might have done the job.

I still haven't got the Tone Profiles right on but its a lot better.

Thanks!