[Asterisk-Users] Syntax for hiding caller ID but still passing ANI?

[John Todd]

I have a question regarding the flags for hiding caller ID presentation:

My customer has a requirement that they are able to specify if 
outbound calls (on a T100P) will have the caller ID displayed or not. 
This could be easily solved, of course, by not setting a caller ID 
when creating the outbound call.  However, the PRI to which this 
T100P is connected _must_ see a valid caller ID, and the caller ID is 
used for billing purposes.

I know that there is the ability to hide caller ID within the Zaptel 
libraries, using the presentation flags.  If set correctly, the 
expected behavior would be that the ANI would be sent to the switch, 
but with a flag that would tell the remote switch to suppress the 
caller ID from being transmitted to the end user.

How does one activate that presentation switch from within a dialplan?

Searching the archives gives me some hints, but no answers. 
Searching the code, I see in channels/chan_zap.c around line 1399 
that the PRES_ALLOWED_USER_NUMBER_PASSED_SCREEN and 
PRES_NUMBER_NOT_AVAILABLE are referenced, but I'm not clear on where 
"l" is set, or even if that is a trigger.  Can someone give me a hand 
on syntax on this?

JT