asterisk users - Apr 2008 - Busy (congestion) signal and cell phones

Hello, all!
I've noticed a peculiar situation and I am hoping someone can shed  
some light on it for me. We have an Asterisk (1.4.18 ) box talking to  
the world via Zaptel on a PRI from a telco (USA). I have an extension  
that returns busy signal (fast-busy or regular busy) (using US tones).  
When I call from a landline or from another PBX, I get a busy signal,  
just like I expect. But when I call from a cell phone, the cell phone  
terminates the call as soon as connection is established. I've tested  
several cell phone models from different providers in the US. Same  
thing happens with calls coming from Gizmo.

I manually changed the tones I send back (with Playtones) to mimic  
Austrian busy tone (picked the first one in the list from  
indications.conf) . Now, from the cell phone and Gizmo alike, I get  
busy tones. So, my questions is:

why do cell phones and Gizmo both detect busy tones and terminate the  
call? Is that a standard behavior? Why don't landlines do that?

Thank you in advance.

Regards,
Mark G.

On Wed, 16 Apr 2008 08:40:42 -0500, Mark Gimelfarb <mark at dawebber.com>
wrote:
> why do cell phones and Gizmo both detect busy tones and terminate the  
> call? Is that a standard behavior?
It *is* standard procedure for a cellphone to terminate a call immediately
it discovers that the called number is busy. It will then, optionally,
initiate its auto-redial function etc.
> Why don't landlines do that?
Because back in the old days there were no intelligent electronics to tell
the user that the call failed. A special "busy" tone had to be
generated to
inform the user that they should hang the receiver up manually. Some
traditions die hard.

-- 
Godwin Stewart - Horwich IT services

What country are you in??  Yes, it is common for cell phones to 
disconnect the call if they receive CONGESTION, but not BUSY.

Horwich IT Services (Godwin Stewart) wrote:
> It *is* standard procedure for a cellphone to terminate a call immediately
> it discovers that the called number is busy. It will then, optionally,
> initiate its auto-redial function etc.
-- 
Consulting for Asterisk, Polycom, Sangoma, Digium, Cisco, LAN, WAN, QoS, 
T-1, PRI, Frame Relay, Linux, and network design.  Based near 
Birmingham, AL.  Now accepting clients worldwide.

I'm in the US, so I was originally using the US tones.
Looks like I'm getting a disconnect with both CONGESTION and BUSY. In  
fact, I wasn't actually using Congestion() and Busy(), I just did  
Playtones() for both of those. There is no reason to send PRI messages  
to cell phones, is there? The way I understand, they do frequency  
interpretation on the incoming tones, just like analog lines do  
voltage variations. So, to test that, I Playtones()'ed (Pardon my  
DialPlan-ish dialect) Austrian busy tones--and the cell phone actually  
played tones back to me. So, to me that means that cell phones look  
for  frequency sequences that they recognize.

Now, here's an interesting observation. If I take an analog phone and  
take it off hook and then call that number from a cell phone, I do  
hear a busy tone. Is that because analog equipment doesn't generate  
the exact tone sequence due to analog limitations? This is in addition  
to my original question.

Regards,
Mark.

> What country are you in??  Yes, it is common for cell phones to  
> disconnect the call if they receive CONGESTION, but not BUSY.
> Horwich IT Services (Godwin Stewart) wrote:
>> It *is* standard procedure for a cellphone to terminate a call
immediately
>> it discovers that the called number is busy. It will then, optionally,
>> initiate its auto-redial function etc.
> -- 
> Consulting for Asterisk, Polycom, Sangoma, Digium, Cisco, LAN, WAN,  
> QoS, T-1, PRI, Frame Relay, Linux, and network design.  Based near  
> Birmingham, AL.  Now accepting clients worldwide.