How does Caller ID work?

For those that are subscribed to Caller ID services the phone company will always display the number if it isn’t blocked or restricted, if it comes through as unknown it usually means the terminating carrier didn’t receive it from the originating carrier.

Caller ID services are subject to the local carriers and their choice to lookup the name in the CNAM database, since this database is not owned by the local phone companies they must pay each time they look into it so they will sometimes cache old names for a while before doing a new lookup or they may not send a name at all and just send a number with the area the number is from.

If you own a phone number that is registered with a carrier you can request that carrier submit a specific CNAM for that number and that is what will be added to the national database and used if the local terminating carrier does a lookup.

You have the ability to out-pulse(send/transmit) any 10 digit Number you would like, however it is worth noting FCC regulation say you must own that number or have permission to use it.

Changing the Caller ID is very simple you can do it on a system wide basis by editing the default.cfa file in the $CFMC/control directory or by editing the study specific cfa files. Caller ID can also set on a record by record basis to deal with “National Call Presence” or being able to always show the respondent a local number if one is available regardless of where the call orginated. Use the “caller_id_loc=<loc.wid>” keyword in the phone header and then assign the location of where the caller ID is located in the record. You can pre process your file against your Caller ID data base if you have one.