Calling Party Number
Outbound calls placed from your phone system are typically identified in one of two ways; by your main number or by the individual DID (Direct Inward Dial) number of the calling extension. We call this outbound Caller ID “CPN” for Calling Party Number. Depending on the type of service, the called party may see number-only or name-and-number. Most modern phone systems allow flexibility in assigning outbound caller id numbers on a system-wide or per-station basis. So, for example, if you are a doctors’ office, you might want your phone system to send your main number on all outbound calls. On the other hand, a real estate office may want their phone system to send the DID number for each individual broker when they make a call.
Redirect
Things get a little more complicated when you forward calls to an off-site number. A forwarded call is known as a Redirect in telecom parlance. The outbound call from the forwarding phone system is known as the Tandem leg or segment. When you forward all calls from your office phone system to your cell phone, what caller id appears on the forwarded call? Your office number or the number or the originating caller? Which do you want it to be? There are differing schools of thought on the subject, but most people want to see the originating caller’s ID, as this gives them the information they need to decide how to handle the call (e.g., answer it or push it to voice mail).
Find Me, Follow Me
With the advent of “find-me-follow-me” features on modern phone systems, this issue has become more important. These features allow a calling party to connect with you wherever you are – at home, on your cell phone, etc. To accomplish this, the phone system essentially holds the incoming call while it tries to locate you. It may ring several destinations simultaneously and deliver the call to the first to answer. Being able to see who is calling is essential to providing the correct response.
Riding Tandem
So, we want our phone system to send the calling party’s CPN on the tandem leg of the call. There is just one problem: we don’t own that number. In order to prevent fraud, carriers typically require that you own any numbers your phone system is sending as CPN. The one exception is on a Redirect.
By the Numbers
Specifically, carriers require that the phone system be compliant with the standards listed below for Call Forward in order for the phone system to send a number not owned by the customer as CPN on the Tandem leg of the call. These standards require that the phone system send both a 10-digit customer-owned number (the “Redirecting Number”), and the 10-digit Originating Number. The Carrier uses the Redirecting Number for validation only, and sends the Originating Number on to the called party as CPN.
Caller ID Blocked!
There is one additional complication on this issue: If the originating caller is blocking their caller ID, the phone system must substitute a customer-owned number (typically the main number) as the Originating Number on the redirected call. The carrier will not accept a Redirect with no Originating Number information.
Here is a graphic showing the process in the network:
The Old Standards
Here are the relevant Standards Specifications:
· Telcordia GR-1310 (Call Deflection for PRI)
· Telcordia GR-853 (ISDN Call Forwarding)
· Telcordia SR-4994 (ISDN PRI Customer Premise Equipment Guidelines)
· ITU Q.953 (Call Diversion)
Are you using call forwarding or find-me-follow-me features on your phone system? What have you decided to use for outbound Caller ID on your phone system? Share your thoughts in the comments.
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