after the sound that is sometimes heard on the telephone line by the caller before dialing in his calling card number. Calling cards calls are billed on your telephone bill and are identified by the calling card number placing the call. Pre-Paid Calling Cards Another type of calling card is a pre-paid calling card. This also is a wallet sized plastic card, but unlike the other type of calling cards, you pay in advance for a pre-set number of min- utes of calling. You can buy these cards in many retail locations like newspaper stands and drugstores. The pre-paid calling card companies buy the service from a local or long distance service provider. Some local and long dis- tance companies also sell the pre-paid cards themselves. Data Communications Circuits and Services Most telecommunications service providers sell both voice and data communications circuits and services, although some 280 The Telecom Handbook CHAPTER 13 are more focused on data. Others may have separate groups of salespeople to handle the more complex and often more profit- able sale of data services. Data communications is a broad term that refers to any type of computer-to-computer communications. Many large organizations with multiple sites set up a data communications network using circuits and related services and equipment from the telecommunications service provider. Data communications services include individual circuits of different speeds or bandwidth, having to do with the throughput capability. Data Communications also refers to networks con- necting multiple sites. Data communications also includes an organization gaining access to the Internet and using its capabilities to communicate among multiple locations. Some telecommunications service providers set up what is known as a VPN (virtual private network) or intranet which uses Internet-like capabilities on the service provider's own network to set up data communications for its customers. Once a data communications circuit or entire network is setup, it is technically possible to