If you use Airtel 3G Dongle (Mine is Huawei E173) on your Mac, and are having issue using the dongel after upgrading to Yosemite, airtel is of little help. They asked me to downgrade the OS to Mavericks!
This is a companion discussion topic for the original entry at https://www.elitmus.com/blog/technology/making-airtel-3g-dongle-work-on-mac-os-10-dot-10-yosemite/