Mobility and Single Number Reach

Mobility and Single Number Reach - the ability to answer your office calls from your cell

Having seen many times where the terms mobility and single number reach were used to describe different aspects of this family of features, I decided to add my voice to this aspect, in the context of Cisco's UC family of products.

When talking about Single Number Reach, usually the meaning is that a call to one's office number will ring on his cell phone (and optionally on other selected devices) simultaneously. By doing so, there is no need to advertise multiple numbers, or to miss calls that came to your desk phone when you were out.

This usually covers the need for most people, but some would like this to also work when a call comes in to their mobile phone. It's definitely doable, but requires support from your mobile service provider. Some service providers can get very creative and plug your VoIP telephony system into their cloud (using a sip trunk), an ability which can be used for much more then Single Number Reach, but is out of our scope here. The standard enterprise telephony system has control on your desk phone and this is where my focus will be.

On the Inbound direction, mobility would mean that your cell phone will ring when your desk phone rings; it will not ring using your data plan as a VoIP call but as a regular cell phone call. Until version 6.x, Cisco Communication Manager had this ability using a dedicated server, version 6.x and 7.x have it as a built in feature.

Outbound calling is also enabled using this ability, allowing Direct Inward System Access (DISA) like ability to the system. This means that you can call from your cell phone to an access number and then dial to a long distance or international destination, using the company lines (which might be doing it using toll bypass).

Before diving into the technical details of this functionality, let's talk about some challenges and requirements with this feature:

  1. PSTN trunks utilization - every call in this scenario, require at least two DS0's (lines), one is used for the normal inbound call (no way to avoid that) and the other is used for the outbound call to your cell device, if you have more then one remote device (a home phone for example), then that's another DS0.
  2. Voice Mail consolidation - how do you make sure your office voice mail will be used when you miss a call and how can you direct all your voice mails into a single mail box.
  3. Caller ID spoofing - how do you dial from your cell phone and present yourself to the callers as the office number, so that when someone returns a call he will call your main number.
  4. Message waiting indication - how can you get an indication on your cell phone when you have a new voice mail in your office mail box (just like you get when there is a message in your cell phone mail box).
  5. Remote service control - we need this service to be optional, where it's turned off during weekends and vacation, and this should be remotely controlled, using voice or data connection.

These challenges are solvable in some cases but not always, I'll address them as we move forward.

How does this works in Cisco's communication manager context? On the inbound it basically works by creating a cell phone pointer in Communication Manager and creating a bridged line appearance between the pointer and your office extension.

If an incoming call is answered using the cell phone, the call is bridged through Communication Manager for the entire call duration (requires two outside lines), this allows the user to pick up the call from his office phone (mid-call).

On the other direction, if a call is answered using the office phone, it is possible to route it to your cell phone, but this will be dialed specifically so the cell phone circuit is not engaged until the user is specifically selecting this option.

Remote control on the service status (on or off) and the ability to dial via the office is accomplished using an H.323 gateway (MGCP and SIP are not currently supported) and a TCL or VXML script that provides the menu options to initiate calls or control the service status.

More on this, for Communication Manager version 6.1, can be found at:

I'm curious to know if and how this functionality is provided with other vendors, any input would be appreciated.

Later, Avner.

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