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How Caller ID Works: Common Questions and Answers

by Kevin Bartley

In this info-packed FAQ post, you'll learn how caller ID works and how you can change your business caller ID information.

Caller ID is a widely used phone system feature that identifies an incoming caller by a name and phone number. The feature isn't perfect, and it can sometimes misrepresent a caller's identity. But for the most part, caller ID is a valuable piece of information. It's offered with just about every commercial phone provider, including landline, VoIP, and mobile phone services.

However, unlike local number portability (LNP), caller ID is not regulated by a governing body such as the Federal Communications Commission (FCC). Rather, the service is essentially a patched-together network of decentralized databases that frequently operate with outdated information.

If your business does not have caller ID set up, it's a good idea to talk to your phone company. Oftentimes, it's one of the first pieces of information you present to a potential customer, partner, or affiliate. Inaccurate or missing caller ID information can preclude people from answering your calls. You're missing out even if you lose just one customer due to something so simple.

To help you navigate some common issues related to caller ID, we put together some of the most frequently asked questions and answers on the subject.

What Is Caller ID?

Caller ID is a phone feature that provides the name and number of a calling party, if available. Caller ID technically only supplies the phone number of the calling party, but its usage as a term has effectively made it synonymous with the calling name, too. The name of the calling party is actually provided by a service called CNAM.

How Does Caller ID Work?

When a call is made, the originating phone switch sends the caller's number. Then, with the caller's number, the callee's service provider is responsible for looking up the caller's subscriber name.

When it was developed, the world was primarily a realm of Plain Old Telephone Service (POTS) lines, and the caller information was tied to the Central Office switch to which the wires were connected. Since there were also relatively few carriers at the time, it was easy to keep track of the caller ID information in one place.

Today, with the prevalence of wireless and VoIP phones, hundreds of local/long distance carriers, consolidations, mergers, and the like, the map has become much more fragmented. Unlike phone numbers and domain name service (DNS), wherein there are internationally recognized databases that are authoritative sources, there is no central authority or regulation for caller ID. No FCC guidelines regulate carrier accuracy, and although federal regulations exist regarding telemarketers and spoofing, carriers can maintain their caller ID databases as they see fit.

How Is the Caller ID Phone Number Determined?

The phone number displayed by caller ID is determined by the calling party. For a landline, the displayed number corresponds to the phone number that's registered to the line. For a PRI or SIP connection, the phone system can actually control what number gets displayed on a case-by-case basis.

How Is the Caller ID Name Determined?

The caller ID name is determined by the receiving carrier. The receiving carrier queries a CNAM database to determine the name registered to the provided phone number.

What Is a CNAM?

CNAM (“Calling NAMe”) is an outside telecom service that phone companies use to pair incoming numbers with names. Unlike phone numbers, CNAMs are not centralized databases. A carrier can choose from many different CNAMs. Each CNAM maintains its own private database on phone number/name pairs in the United States and abroad.

How Many Characters Does a Caller ID Display?

A caller ID outputs up to 15 ASCII characters to display a name, and a typical display name is 9 to 12 characters. The phone number is usually displayed as a ten-digit number.

How Do I Change My Business Caller ID Name and Number?

It's possible to request changes to your caller ID name and phone number, with varying layers of customization, depending on your phone provider. Some providers require you to call a customer service representative to make a request. Other providers allow you to change caller ID data directly from an online interface.

Landline Phone Numbers

The caller information for Plain Old Telephone Service (POTS) lines is tied to the physical wires connected to the phone company's central switch. For this reason, analog lines will always display the number that's associated with the line itself.

You can change the display name for an analog line by requesting a name change for the number associated with that line. This process will likely involve calling your customer support line and speaking to a phone company representative to request a manual change.

VoIP Phone Numbers

Unlike landline services, VoIP services allow you to modify the caller ID display number in addition to the name. Some providers even allow you to configure this information directly via a web interface, without needing to contact a support representative.

Hosted VoIP companies typically send caller ID name updates to the central CNAM databases within 24 hours. As far as phone numbers go, VoIP lines do not have the same wire/number pairing as analog lines do. A VoIP service can usually pass any phone number of your choosing to the person you're calling.

However, this number will still get cross-referenced with the caller's CNAM service, so the CNAM name associated with that number will be displayed. VoIP services do pass a name identifier with caller ID info, but most carriers do not display that data unless it's a SIP to SIP (extension to extension) call.

Most landline services apply the same name and phone number across users, but some VoIP providers allow you to apply unique caller ID name/numbers to individual users within the phone system. This feature is helpful for security, caller authentication, and customization purposes.

Why Is My Caller ID Info not Updating?

Ultimately, it comes down to how quickly the new data is related to a CNAM and how fast the other carriers pick up on the change. Getting the data to the CNAM can take anywhere from a few minutes to a few days; getting it to the other CNAMs can take much longer.

If you call someone and her carrier happens to be on the same carrier or on the same CNAM, then your caller ID info should update almost right away. However, for other CNAMs, the updates could take up to several weeks.

The best you can do is to make sure that your phone company has updated your information to its CNAM and then wait for the changes to circulate. Unfortunately, there is currently no expedited option.

Can Caller ID Information Be Faked?

With Internet calling technology, caller ID is prone to camouflage and spoofing. The most important thing to remember is that caller ID is not a feature that confirms a caller's identity. It's really an estimate designed to give you context as to who is trying to contact you.

Caller ID: Who's Calling?

Caller ID remains a staple of every type of phone service. That's why you should do your best to make sure your business gets represented properly by caller ID information. Otherwise, if the person you're calling finds your name unrecognizable or unprofessional, he will simply avoid the phone call. This can cost you business and respectability.

Because caller ID is not federally regulated, you never know how long it will take before your new information is properly displayed on all of your outbound calls. However, it is still a valuable and worthwhile investment to go through this process to ensure that your business is accurately represented wherever possible. Make those characters and digits count.

How Does OnSIP Caller ID Work?

We offer caller ID for our OnSIP customers, and we don't charge extra for it. We offer this feature by querying a reputable CNAM database.

On an inbound call, the call is sent to us, often from the Public Switched Telephone Network (PSTN), with a ten-digit number sent from the caller's provider. We take that number and look it up in the CNAM database to which we subscribe, and if it’s associated with a name, we send it to the OnSIP callee's registered phone(s) for display. Usually, the name is between 9 and 12 characters. If there is no information on file, we send a best approximation of the geographic area for the phone number (e.g., New York, NY).

Outbound caller ID works the same way: We send the number to the PSTN, and the callee's provider does the lookup against its database, which may not be the same as ours.

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If the callee's provider uses the same CNAM database as we do, chances are the caller ID name you have set in your account or user record will accurately appear there. We send all subscriber updates that OnSIP users make to our CNAM provider every night, and the changes can show up quickly—in as little as 24 hours. However, the information may take a while to propagate to other CNAM databases. So if an OnSIP customer updates her caller ID settings, the change will be quickly evident if she calls someone whose telephone service provider uses the same CNAM database.

Unfortunately, if the callee's provider uses a different CNAM database, the change may not be evident for weeks. When a call is made to a cell phone, most times the phone does a lookup against the contacts in the phone’s address book, and if the number isn’t there, will display “unknown.” This varies across providers, so check the service level of the individual provider for exact information.

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