In this age of much hyped cloud IVR, there are still some users who still use on premise Interactive voice response system on analog telephone lines. In one typical and unpredictable problem while using analog line is, sudden high voltage in the telephone line and damaging the CTI board. While this problem is not frequent and many CTI boards are equipped to handle this kind of voltage fluctuations, still it may happen anytime anywhere and there seems to be no permanent solution to it!
Recently, I had learned similar experience while speaking to an Analog IVR user. IVR systems works fine but suddenly it stops working as the CTI board stops working, unable to sense incoming calls. Finally, they had found a solution to it, by using FCT ( Fixed Cellular terminal). yes, they have changed their analog landline number to mobile phone number which is connected to CTI board. The previous landline number was forwarded to this mobile number and the existing system kept working, callers did not realise about the changes which had taken place!
With use of FCT, over all cost of the IVR increases, but the investment in FCT initially is more worth the trouble in future for downtime of IVR system.
Most probably, the voltage issue will not happen if one is using inhouse PBX systems but may occur when on is using public telephone system where copper wires are being used.
Either way, most probably, use of FCT is the best solution to avoid such voltage fluctuations issues for analog IVR systems using analog CTI boards, though I would always recommend everyone to use a Digital PRI and digital CTI board which has many advantages.