Thank you for your reply. but I tried all disconnect supervision types but no luck

You need to configure the tones explicitly for your country.

And, some IOS versions have bugs that prevent it from working.

I am using 2851 IOS version:12.4(24)T

I searched bug toolkit and I found the following bug:

CSCsx42760 Bug Details:

Need attention tone detector for supervisory disconnect

Symptom:

Inability to disconnect on the US 'offhook alert' or 'attention tone'. This tone is used to alert a user that the phone is offhook, after the phone has been offhook for an extended period of time after the other party has hung up.

Conditions:

The tone is made up of 1400 Hz, 2060 Hz, 2450 Hz, and 2600 Hz. This tone is sometimes found as a disconnect tone in areas that do not have any other supervisory disconnect method, and is the only form of disconnect notification.

This bug is to introduce CLI to offer an ability to disconnect on this tone.

Workaround:

None.

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCsx42760&from=summary

but I am not in US

Inability to disconnect on the US 'offhook alert'

Do you think this is the problem???

No, the problem is that you need to configure the tones for your specific country and pstn.

I already have configured them

this is the configuration:

voice-port 0/3/0

supervisory disconnect dualtone mid-call

supervisory custom-cptone STC

no battery-reversal

input gain 14

output attenuation -6

cptone SA

timeouts call-disconnect 5

timeouts ringing 5

timeouts wait-release 5

timing hookflash-out 50

connection plar 5003

caller-id enable

I do not see the custom-cptone configuration.

could you please give me the commands for this?

voice class custom-cptone

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t2/feature/guide/ft_ansds.html#wp168445

I already have added the voice class but still the same problem.

any suggestion??

Wrong tones, or buggy IOS.

Thank you too much for your response:

how I can know the configuration for:

voice class custom-cptone XXXX

dualtone disconnect

frequency

cadence

I used this site:

http://www.3amsystems.com/wireline/tone-search.htm?start=0&kTone=10

to determine the frequency and cadence.

then under the voice port I added the following:

supervisory custom-cptone XXXX

Is there any thing else before upgrading the system???

That seems all good, sometime actual tones don't match database, in which case you have to record and frequency analyze, kind of tedious process.

can you give me more details. how I can record and analyze the frequency?

do you know some program to do this??