[asterisk-dev] Question about end mark of the Called partey number

sky earth tian00di00 at live.com
Sun Oct 11 23:17:43 CDT 2009

Hi Pavel,


Thank you very much for you information!


As we know now that an ST is appended to the end of the called party number, a further question is: why is it appended? Is it used to indicate that complete called party number has been sent? 


When overlap signaling is used, when enough digits have been collected to identify the next exchange, an IAM is sent to the next exchange along the route to the called party, the remaining digits are sent in subsequent SAM messages. I guess that the ST address signal is used specifically for an SAM message  to indicate whether it is the last one of a series of SAM's preceded by an IAM. 


Do I make a right guess? I failed to find clear descriptions of the usage of ST signal address in the ITU Q series standards. I hope that you or someone else will kindly help me out with this issue and refer me to the standard that documents the usage of the ST address signal. 


Thanks again and good luck!








> Date: Sun, 11 Oct 2009 16:34:19 +0200
> From: patrol at sinus.cz
> To: asterisk-dev at lists.digium.com
> Subject: Re: [asterisk-dev] Question about end mark of the Called partey number
> > Hi guys,
> > 
> > I am reading libss7 source code and I notice that when ITU-T version of SS7 
> > is used, a hash mark '#' is appended to the called party number sent with 
> > IAM or the last SAM message. But according to section 3.9 of ITU-T Q.763, I 
> > think an Address signal ST with the binary value 1111 should be sent 
> > instead! Why is there such a difference? Any of you please kindly help me 
> > clear this issue, thank you very much!
> > 
> > Regards,
> > 
> > Tian 
> > 
> Hi Tian,
> you're right that in ITU.T ISUP the number has to be terminated by 0x0f.
> However, I thinkt libss7 is doing it well.
> In isup_set_called(), it adds '#' to the end of the number.
> Then, in called_party_num_transmit(), it calls isup_put_number() to insert
> the number to the message. And isup_put_number() calls char2digit(), which
> converts '#' to 0x0f.
> Regards, Pavel
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