Sequential Ringing is an advanced form of call forwarding. Unlike traditional call forwarding, sequential ringing goes to multiple phones, and can be programed with specific rules. Sequential Ringing is a great tool for business, because business associates only have to know one number to reach you.

When sequential ring is activated, an inbound call will ring one phone, then another, and another, until the call is answered. The most common ring sequence is to route a call from a desk phone to a cell phone to a home phone, then to the voicemail box. But, there are many variations. Many, but not all, business VoIP providers allow forwarding to up to three phones and that is how they define a “user” for billing purposes. The user configures how many times the phone will ring before moving on to the next phone. The voicemail box is usually last because it will definitely answer the call.

Sequential ring can also be used to ring several different people if the intended caller is unavailable. If Andrew at accounting is away from his desk, after two rings the phone can go to Barry, and if Barry is unavailable, then the call can go to Carol, and if Carol is unavailable, then the call will go to Andrew’s voice mail box. There is no need for Andrew, Barry, and Carol to even be in the same geographic area. Another common configuration is to have all unanswered calls be routed to the office receptionist.

There are many ways in which sequential ringing is different from regular call forwarding. One is that calls can be set to go to ring groups, so, for example, if you want to reach Jose in sales and Jose isn’t available, the entire sales department has a chance to answer the call. Another is that call routing rules can be changed depending on the time of day. Also, the system can be configured to that the caller can press a number (or # or *) to skip straight to voice mail.

Sequential Ringing is made possible because of the Session Initiation Protocol. A request (call) is made to the SIP proxy server, which then forwards the request to multiple addresses either parallel or in sequence. If the request is configured to send the request in parallel, all phones ring simultaneously, and if the request is configured to be sent in parallel, the phones ring in sequence. This feature is called “SIP forking.”

Additional Reading

The 10 Hottest Cloud Phone System Features Right Now & Who’s Got Them
What Is Simultaneous Ring?