A workaround to tell PBX sending calling number when integration with Cisco router

ds0-group 0 timeslots 1-15,17-31 type e&m-immediate-start dtmf dnis  


when trying to integrate PBX with Cisco router，we use csim start xxx  to test call connectivity，but call fails when using physical phone. "dtmf dnis" is key word to force PBX sending calling number.