Mobile Twinning is a feature on many business phone systems, or PBXs, that allow a user to link an external number to their desk extension. The external number is typically a cell phone, hence the term “mobile twinning” or “cell twinning”.
This means that whenever your desk phone rings, so too will your “twinned” phone. You can choose to answer the call on either phone at that point. If you don’t answer the call at all, your office phone system will pull the call back and put the caller in your work voice mail.