Special thanks to Eric Phipps and Dave Jodhan, NOC Technicians, for providing the information and diagrams in this blog.
One of our customers had an interesting question that concerns setting up group calls and call forwarding:
Can calls be forwarded to an external line like a cellphone if there are multiple devices registered to the same SIP address?
OnSIP has a unique feature that allows any number of user agents (phones, soft phones, etc.) to be registered to the same SIP address. For example, you can have one phone at your cubicle, one at your home office and also a soft phone to take calls on your laptop, all registered to your extension. When a call is made to that extension, all three devices ring, allowing you to take the call on any of them. In usual cases, if the call is not answered on any device, the call is forwarded to a voicemail box associated with that extension.
However, when you've set up one of your devices to forward the call to another number, say your cellphone while traveling, and you are unable to answer the call, one of two things can happen:
Let's say that -
x is the number of rings it takes before a caller is sent to your OnSIP voice mailbox. x can be set in the OnSIP admin portal.
y is the number of rings it takes before a caller is sent to the voice mailbox on your cellphone. y is determined by your cellphone carrier.
If your cellphone's voicemail box has not been set up, the caller is sent to your OnSIP voice mailbox after x rings.
If your cellphone's voicemail box has been set up and y is less than x (the number of rings it takes to trigger your cellular voice mailbox is less than the number of rings it takes to trigger your OnSIP voicemail box), your caller will be sent to your cellphone's voice mailbox. Our system understands that the call has been answered, albeit by your carrier's voicemail.
The diagram here will help understand how the call is routed when a call is made from an external number to user B.
Calls made to a group are similarly routed: Let's say your sales department extension is configured to ring users A, B and C, and if the call is not answered, the caller is able to leave a message at the sales voicemail box. If one of the users, say A, has call forwarding set up to his/her cellphone, then the call is deemed answered if the cellphone voicemail box is reached before the sales team's voicemail box.
If you want calls to your extension forwarded to your cell phone, but you prefer not to have your callers leave messages on your cellphone voicemail box, configure your OnSIP phone to direct calls to your voicemail box after fewer rings than your cellphone would. This is easy to set up on the OnSIP admin portal.