the dialed number to the database 58 in step 110 and in step 111 acknowledges receipt of the signal to the originator for example by generating a brief audio tone the number is added to the database 58 in step 112 and the dnc server 56 waits for an on hook signal and ends processing in step 114 if a command to add the number to the database 58 is not received then the call continues in step 113 until the end of the call in step 114 referring now to fig7 an illustration of a sample file containing dnc identifiers in particular telephone numbers will be described the dnc numbers in this embodiment of the present invention are stored in binary bit map files this is only one possible implementation of such a database other database structures such as a relational or an object oriented database may be used the database may be accessed using simple file read and write commands or by a database query language such as sql in this embodiment of the present invention there is a bit map file for example bit map file 700 for every area code that has dnc numbers all bit map files 700 are 1 250 000 bytes in size as shown in 701 each exchange within the area code is allocated a 1 250 byte block as shown in 702 which contains 10 000 bits as shown in 703 these bits 703 are mapped to the last four digits of the phone number 0000 9999 the system of.