[asterisk-users] How do I issue a Flash to Zap (PSTN) from SIP?

[Jim Duda]

I've seen a few posts on this issue, however, no definitive answer.

My PSTN is connected to Zap/4.  I have simple Call Waiting service on 
the PSTN line.

All the other phones are SIP clients.

When I'm on an Zap/SIP connection and another call comes in, I can hear 
the Call Waiting Tone on the SIP line.

How can I issue a Flash/Hook to the Zap line in order to accept the 
other call?

Also, is there any means to get Caller ID for the other call?

I've seen posts that I can use *0 or *3 to send the Flash/Hook, however, 
that doesn't work for me.

I realize there is a Flash( ) Dialplan function.  How can I use this 
Function in the Dialplan with a call which is currently in progress?

Any advice is most appreciated.

Jim