fxo - disconnect delay (10 sec) issue

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Nov 13th, 2008
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1. case1. cell phone-PSTN(carrier)-analog line-analog phone

2. case2. cell phone-PSTN(carrier)-analog line-fxo(2811)-IP phone

when hang-up the call by cell phone, there is no disconnection delay for Case1 but 10 seconds for Case2.

Q1) what's difference between Case1 and Case2? Is the FXO operates different way than Case1?

Q2) for Case2, via debugging (debug vpm signal), I receive disconnection command 'fxols_offhook_disc' from Carrier 10 seconds later when the cell phone hang-up. can I control the disconnection timer before receive DISC from Carrier?

Thanks in advance,

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allan.thomas Thu, 11/13/2008 - 14:19
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This is a common problem with FXO modules, the FXO module will appear to the local switch as a normal phone, and therefore the switch will never disconnect as the phone is expected to hangup.

The FXO port on the other hand expects the switch to tell it when to hang-up or remove the battery to indicate on-hook.

There is no guarantee that a near-end or far-end FXO port disconnects the call once either end of the call hangs-up.

To overcome these disconnect issues you will need to consider configuring supervised disconnection on your voice-ports, if not already. Can you post your configuration?

There are different supervisor disconnect methods.

Please review the following document URL:-


Hope this helps.


Pls rate helpful posts.

cjrchoi11 Thu, 11/13/2008 - 19:53
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Hi Allan,

here my scenario,

1) PSTN user dials FXO port and call setup

2) hang-up the call by PSTN user

3) takes about 10 seconds until receiving 'fxols_offhook_disc' from carrier

as per TAC, there is no way to control the delay until receive 'disconnect command' from Carrier and the 'supervisor disconnect' method is valid after receiving the 'disconnect command'. ->correct please if you think TAC is wrong.

Can I control the gateway to minimize the disconnection timer before receive 'disconnect command' from carrier?




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