[Asterisk-Users] Strange beeps in Calls

[Kai Militzer]

Hello list,

we are experiencing a strange problem here. We offer SIP-Accounts to our 
customers. Our asterisk connects via SIP to a remote PSTN gateway of a 
TelCo.

In some outgoing calls (SIP to PSTN) the called party suddenly hears a 
very loud beeping noise that goes on until the call is hung up. During 
the beeping the called party cannot hear the calling party any more.

There seems to be no regularity in this behavior as sometimes this 
happens shortly after the call is established, sometimes after 20 
minutes or more into the call. Asterisk gives not error messages or 
anything else. The only thing we can see is, that the call gets hungup, 
which probably is because of one party hanging up (the call is not 
usefull with the beeping).

The problem must be somewhere in the RTP-Part of the call, but I have no 
idea why. Our service provider tells us, that he neither can see 
anything on its PSTN gateway.

If anyone on this list has experienced a similar behavior or has any 
explanations for this we would be very grateful.

Best regards
Kai