You should use an alphanumeric data type to hold a telephone number in a database. ADSL transmits analogue signals over ordinary telephone lines. ISDN is an analogue link. The DBA is concerned with database access and integrity control. A relationship between two tables is established by means of a foreign key. There are no secure methods of transferring data across the Internet. A firewall is used to protect against attacks on the Internet. NOS stands for Network Open Source. Date is a database field type. A link between two database tables is called a relationship. Copyright law covers software piracy. SAP is an example of system software. Fibre$-$optic signals get weaker over long distances. Source code refers to program code that is produced by a compiler. It is a good idea to use your date of birth as a password as you will never forget it$.$ All ISPs are connected directly to the Internet Backbone. In the case of a LAN, the computers on the network may be located in different cities. In a star network each computer is connected to a central device called a Bus. Google is a Web browser. Internet companies are known as dot bombs.