Im running 3cx 10 sp5 with cisco spa525 phones. Using a patton 4960 with a PRI for dialtone. I have them using 9. as a prefix to dial out. I have their mobile phones setup as 9xxxxxxx. When I set their phone to ring their mobile and desk at the same time, the desk phone only rings once, then the mobile starts ringing. It happens for every extension. I have never seen it do this before. The only modifications I have made are From the 3CX Management , click on the Settings node and then on the Advanced sub-node Click on the ‘Custom Parameters’ tab In the ‘Filter by Parameter Name’ type ‘allowuse’ (no quotes) and click on the ‘Search’ button One entry appear, with a value of ’0′. Change this to ’1′ (no quotes). Click on Apply followed by OK. This is so that the ring group members can take more than one call at a time. All extensions are set to access more than one call at a time.