tone from the GSM module is not continous,though you can be able to make a call from the module directly.This brings about a second problem that if you feed this signal into a PABX it is suppressed at the output terminals of the phone line you can not be able to make a call at all.I have checked the settings for GSM module line in the PABX and are correct.NB the other GSM module for another line is working properly