In the case of simple hardware devices like the pager, the address is simply the electronic serial number (and later IMEI/MEID) in its firmware, or physically manufactured into its circuitry.
Addressing and encryption are used together for conditional access to different TV channel bundles which a pay-TV customer has or has not paid for.
Even physically separate devices are now addressable, such as to enforce revocation lists for digital restrictions, or to use the former DIVX DVD video rentals, although the latter only used its identity to "phone home" for billing purposes.
At the Headend, the signal may be manipulated by being scrambled, encrypted and having authorization codes attached thereto by a Scrambler.
The billing system or BSS typically manages products and services, customers and addressable equipment such as the converters and controllers.
Based on the comparison, the customer's STB may or may not be able to descramble the signal and view the content or Television Program.