Asterisk 1.6.2 waitfordialtone not working

I am using asterisk 1.6.2 with TDM400 clone.
I have spent more than two days to try to fix an issue. Before giving up, this forum is my last hope.

The problem :

  1. With my PSTN Telco Company only the caller can hangup a call. This fact has been checked using plain phones.
  2. Assume somebody calls my box and I decide to hang up. => Asterisk will effectively hang up (this fact has been checked). But, because I am not the caller, the call will not be terminated until the remote party (caller) hangs up. This is not really a problem because after 90 seconds the line will be hangup regardless of the state of the remote caller (using CPC).

My issue occurs if before the 90s I attempt to dial a pstn phone. Because the line is not yet hang up, the remote party (who has not yet hang up for any reason) will listen my dtmf tones while dialing.

The solution that I tried to use is through the new parameter in Asterisk 1.6.2 : Waitfordialtone.
Before dialing, asterisk will detect if there is a dial tone on the line.

i) By default the value of this parameter is 0 ms. In this case, I assume that dial tone detection is disabled. In this case, I can perform outgoing calls.
ii) If I change this parameter to 10000 ms (10 secondes) then asterisk open the line and wait for 10 seconds and the message (all lines are busy) is played. my explaination is that ASTERISK DID NOT DETECT THE DIAL TONE.

So, I tried to check if my international settings were correct.
I took my scope and measured the frequency of the dial tone. I found a continous 425 Hz sine wave.

I then took a country whose dial tone meet these data (result in indication.conf). … IN VAIN.

I really did’t find a way to make Asterisk detect dial tone.

Please Help !
Thank you

This is why PABX lines normally use ground start. It sounds a though you either have loop start, or you haven’t configured properly for ground start.


Clones of the TDM400, as well as legitimate TDM400 and TDM410 cards, are loopstart only.

In that case, he’s going to need disconnect supervision. I presume that removing battery for disconnect supervision will work, if configured for “kewl start”. Will asterisk keep the line busy until it gets a line reversal disconnect supervision, if that is configured?

Yup. Configuring for kewlstart is “loopstart with disconnect supervision.”

The Wikipedia entry for Kewlstart suggests that it only works for battery removal, i.e. not for line reversal.

In any case, we have to establish that the PTT uses any sort of disconnect supervision. Loop start is normally used on domestic lines, where supervision is not a priority.

Thank you David an Malcom.

My Telco operator uses loopstart. I checked with a phone with a led. The phone is powered by the operator line and I noticed that the led didn’t switch off when the person who I called hanged up => There is no disconnect supervision.

At this stage, I want to make the option “waitfordialtone” work.
Have you ever tried this option ?

Any help please ?

Thank you.


Does your telco have any options to turn any disconnect supervision (battery drop) on, for your line?


There are two evidene :

  1. If somebody calls me and then HE hangs up, my box will flawlessly detect busy tone and will hang up. My line is immediately ready for a new outging call.

  2. if somebody calls me and then I hang up, my box switch will open the circuit but after closing the circuit (Another outgoing call for example) I don’t have a dialtone. Rather, the person who called me is still here conversing with me. (ie) if somebody calls me I have no way to get the line hang up and ready for a new outgoing call before 90 seconds. After this delay, the line is effectively hang up and ready for a new outgoing call.

This is the reason for which I want to detect dial tone. If the dial tone is not detected on line 1 then the box will choose line 2.

Now my issue concern waitfordialtone option that fails to detect my dialtone and I get “All lines are busy” message.

Thank you again.
Thank you.

You are repeating the question, which I think we both understood. The UK landline phone system works the same way.

What we are suggesting is that the best solution is ask your PTT to provide you with a more appropriate service, rather than trying to work round what is basically a domestic phone line service.

I will follow your advice.
I will contact them and ask for a better solution.