There are two major types of caller ID cards, and a number of different companies produce each of them. One of the most common types of cards is needed to provide caller ID services to additional phones that are part of a large network. These cards are often available from phone manufacturers, and allow an extensive network of phones to function together properly and display accurate information about received calls. There are also some caller ID cards that can be used for caller ID spoofing, which is the process of making a person receive a call that appears to come from a number other than the one from which it truly originates.
Caller ID cards typically refer to pieces of technology similar to computer components, or to cards used in caller ID spoofing. Hardware cards are often about the same size as an audio card or internal modem that can be installed into a computer. These caller ID cards are installed as part of a phone system that includes numerous phones together on a network.
Many of these types of systems are used by businesses with a single network on which a number of phones are connected. In order for some features of these phones to function properly, additional hardware may be required. This includes caller ID cards that can be installed onto the network to ensure that each phone is able to receive and properly display information about incoming phone calls.
The other common type of caller ID cards are small, plastic cards similar to calling cards used by people to make long distance phone calls. These include a phone number for the service offered on the card, along with a Personal Identification Number (PIN) that is used with the card. Someone can call this phone number, input the PIN, and then use the service associated with the card to alter the number that someone sees when receiving a phone call. This can be done in a number of different ways, but often includes the use of Voice Over Internet Protocol (VoIP) software to route calls through a computer system.
When people use these types of caller ID cards and input their PIN, they are then typically prompted to enter the phone number they wish to dial and the number they wish to appear as. The service then connects the phone call to the desired number, and supplies the second number as the source of that call. Someone receiving the call then sees the supplied number, rather than the actual number a person is calling from, on his or her caller ID. This process is referred to as caller ID spoofing and may be illegal or strictly regulated in some areas.