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Walkthrough Wednesdays

FXS getting "Dial Tone" when the opposite party on-hooks.

I have CUCM 7.1.5 and 2921 gateway with VIC3-2FXS/DID card.

SCCP is up and running for FXS support.

More or less everything is working but I nioticed strange thing:

Whoever initiates the call between analog phone on FXS port and IP Phone, when IP user goes on-hook then user at FXS hears in his set "dial tone" for 5 seconds and after that goes the voice announcement "Your call can not be completed as dialled....". Only after this procedure he hears fast busy tone.

How could it be? CUCM should supply a "Busy tone" to the FXS port in this scenario.

As analog user does not do anything (just listen to the handset) then it means that CUCM does some routing for him in such a case?

Configuration is simple:

voice-port 1/0/0

ring cadence pattern02

no battery-reversal


cptone RU

timeouts initial 60

timeouts interdigit 60

timeouts ringing infinity

timing hookflash-in 600 80

timing digit 50

impedance 600c

caller-id enable

The trace on FXS port shows the following when IP set user goes on-hook::

C2921-VOIP-GW#htsp_call_feature:feature 6

*Jul  5 14:35:11.247: htsp_process_event: [1/0/1, FXSLS_CONNECT, E_HTSP_ONHOOK_OUT]fxsls_offhook_lcfo

*Jul  5 14:35:11.247: [1/0/1] set signal state = 0xC timestamp = 0

*Jul  5 14:35:11.247: dsp_set_sig_state: [1/0/1] packet_len=12 channel_id=129 packet_id=39 state=0xC timestamp=0x0

*Jul  5 14:35:11.247: [1/0/1] set signal state = 0x4 timestamp = 750

*Jul  5 14:35:11.247: dsp_set_sig_state: [1/0/1] packet_len=12 channel_id=129 packet_id=39 state=0x4 timestamp=0x2EEhtsp_call_feature:feature 34

*Jul  5 14:35:11.247: htsp_process_event: [1/0/1, FXSLS_CONNECT, E_HTSP_STOP_RINGING]htsp_call_feature:feature 34

*Jul  5 14:35:11.247: htsp_process_event: [1/0/1, FXSLS_CONNECT, E_HTSP_STOP_RINGING]


Just found out . It is a "feature" so it is supposed to work like that by default.

Here is a description

To disable it and send "Busy tone" configure dial-peer for FXS

no tone dialtone remote-onhook

tone busytone remote-onhook

This helps to send busy tone but still after 5 sec goes recorded announcement. Anybody knows how to disable this?

I know this timeout is "Off-hook to First Digit Timer" in Service parameters but why CUCM waits for digits to be dialled? It should just wait for user on-hooking


Hi Alexey,

Four years after your last post, are you maybe around?

I have the same issue while using a VG224 controlled by MGCP. When the IP Phone side hangs up, the analog adapter "hears" a dial tone (like if the VG224 gives a new occasion to dial out), and after the off-hook timer, plays the announcement.

Did you figure out why the VG224 tries to open a new call occurence instead of simply waits for the analog device to hang up?

Thank you for your feedback.


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