Putting your office telephone extension onto your smart phone

In our firm’s work-from-home setup, everything is Voice over IP (VOIP).  This means it is super easy to make it so that a work-from-home employee can have a phone on their desk at home that works exactly like the phone on their desk in the office (blog article).  But what is very interesting to think about is that if you have a VOIP telephone system, any employee who wants it can also have his or her office phone extension operating on his or her smart phone. 

The way this works is that any employee can install a VOIP app on his or her smart phone.  Our favorite is the Grandstream Wave app, but another popular one is called Zoiper and there are many other good VOIP apps.

Within the app, you configure several things:

  • the IP address or domain name of the SIP server (in our case, our PBX)
  • the SIP user ID (which in our system is the extension number)
  • the SIP password for that user ID (preferably something that is not easily guessed)

That is the bare minimum of what you would configure.  In addition, you will want to configure a few more things:

  • a NAT traversal setting such as a “keep-alive”
  • a setting for encryption of the call setup and call management communications (namely a SIP setting of “TLS”)
  • a setting for encryption of the audio talk path (namely an RTP setting of “SRTP required”)

In our PBX, we can configure each phone extension to permit multiple “registrations”.  This allows us to set things up so that if someone dials my office telephone extension, the call will ring in multiple locations.  In my case it rings on my desk in the office, and it rings on a desk phone in my home office, and it rings on the app on my smart phone.  With multiple registrations, the way it works is that whichever telephone answers the call, that telephone will handle the call and the call will stop ringing on the other phones that were ringing.

The main thing is that this permits a work-from-home person to answer calls on the office phone system in a very convenient way even if they are not at their work-from-home desk.  

Another way that this can be helpful is that on my smart phone, I can use the VOIP app and dial the extension number of anybody in my office and the call goes directly to that person.  I can dial an outgoing call for example to a client or foreign associate, and what they will see on their caller ID is my office telephone number (not my cell phone number).

One nice thing about a VOIP app such as Wave or Zoiper is that it will show a little padlock on the screen during an encrypted call, to let you know the call is encrypted.

Do you use a VOIP app on your smart phone?  Which one do you like the best?  Please post a comment below.

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