External calls sometimes connect, sometimes don't!

Although we’ve just about got all of the functionality that we need from our Asterisk box, I’ve noticed a couple of problems when people phone any of our external numbers.

When people call using a mobile, the first time they never get even to the ringing, just silence, the next time they phone immediately after that, they will be able to get connected. I’ve also heard about this from landline phones, although not as often. Has anyone come across this before?

John

Please try to read your own posting and then tell us what did you understand about problem described in posting.

Hwo rings.
How it is connected.
What kind of phones use ringer.
How you ring ot external phnes - do you use PSTN? Or T1/E1/ISDN or may be some of 1000s SIP/IAX/H323 providers?

[quote=“bira_more”]Please try to read your own posting and then tell us what did you understand about problem described in posting.

Hwo rings.
How it is connected.
What kind of phones use ringer.
How you ring ot external phnes - do you use PSTN? Or T1/E1/ISDN or may be some of 1000s SIP/IAX/H323 providers?[/quote]

The phones are all SIP, the external connection is via ISDN. making a call from the SIP -> ZAP is fine, it calls out every single time. When external calls
ers make a call from mobiles, it takes 2 calls before it registers on the console. In other words, if I call one of external numbers from a mobile and watch the console, the first time I phone I get nothing on the console, the phone doesn’t ring and the call is never made. If I make another call immediately after the first failed call, the call goes straight through and is displayed on the console.

John