Missed call communication protocol

Richard Bennett richard.bennett at skynet.be
Thu Feb 8 11:16:04 CET 2007

On Thursday 08 February 2007 09:01, Alexandre Ghisoli wrote:
> > Sorry to throw a spanner in the works but I'm not sure that this will
> > work here. It may work in other countries. I think I heard about it
> > working in the US.
> I'll second that for switzerland.
> When you subscribe for a E1 channel or direct VoIP trunk, you cannot
> send full e.164 number, but only the last digits that stick in the range
> of number the telco gave (rent ?) to you.
Now that you mention it I have noticed that sometimes to during testing, but 
not always.

> Now, for law enforcement, you are *NOT* allowed to change your clip on
> the network.
Ok, if that is the case then using the CLI won't fly beyond skunkworks anyway.

> 2/ For ISDN network (Q.931 signaling), use of the UserInfo field, on the
> signaling session (yes, you can send some byte when the phone is
> ringing, without charge)
Ok... Are you sure you don't mean the 'Display' field in the ISDN SETUP 
message? I can't find references to a UserInfo field in q931.

Apparently the Q.931 protocol limits the maximum length of the Display Field 
information element to 44 octets, that should mean one can use 44 characters 
for a message without opening the line, which would be fine.

It seems that GSM should support the full range of ISDN messages,
so I'm wondering, why is no one using this for enhanced caller-ID, or similar 
applications. Where's the catch?


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