Editing Caller ID (section)

==Calling-line identification==
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In some countries, the terms '''caller display''', '''calling line identification presentation (CLIP)''', '''[[call capture]]''', or just '''calling line identity''' are used; call display is the predominant marketing name used in Canada (although some customers still refer to it colloquially as "caller ID"). The concept of calling number identification as a service for POTS subscribers originated from [[automatic number identification]] (ANI) as a part of toll free number service in the United States.

Caller ID and ANI are different and distinct services. ANI was originally a service in a non-electronic central office that identified the telephone number of the line from which a call was originated. In addition to the caller's telephone number, caller ID may also transmit the subscriber's name, when available. The name can be passed on by the originating central office, or it is obtained from a line information database by the terminating switch. If no name is available, the city, State, Province, or other designation may be sent. Some of these databases may be shared among several companies, each paying every time a name is "extracted". It is for this reason that mobile telephone callers may appear as "WIRELESS CALLER",{{cn|date=June 2023}} or the central office location of the number.

If the call originates on a POTS line (a standard loop-start line), then caller ID is provided by the service provider's local switch.  Since the network does not connect the caller to the callee until the phone is answered, generally the caller ID signal cannot be altered by the caller.  Most service providers, however, allow the caller to block caller ID presentation through the vertical service code ''*67''.

A call placed behind a private branch exchange (PBX) has more options.  In the typical telephony environment, a PBX connects to the local service provider through Primary Rate Interface (PRI) trunks.  Generally, although not absolutely, the service provider simply passes whatever calling line ID appears on those PRI access trunks transparently across the Public Switched Telephone Network (PSTN).  This opens up the opportunity for the PBX administrator to program whatever number they choose in their external phone number fields.

Some IP phone services (ITSPs, or Internet Telephony Service Providers) support PSTN gateway installations throughout the world.  These gateways egress calls to the local calling area, thus avoiding long distance toll charges.  ITSPs also allow a local user to have a number located in "foreign" exchange; the New York caller could have a Los Angeles number, for example.  When that user places a call, the calling line ID would be that of a Los Angeles number, although they are actually located in New York.  This allows a call return without having to incur long distance calling charges.

With cellphones, the biggest issue appears to be in the passing of calling line ID information through the network.  Cellphone companies must support interconnecting trunks to a significant number of wireline and PSTN access carriers.