VoIP For Dummies

Appendix B

Glossary

Numbers

911: The standard number for emergency telephone calls made over the public switched telephone network (PSTN) in North America. See also E911.

A

access: A generalized term referring to the physical means (such as POTS line or T1 line) through which a carrier company provides telecommunications services to a customer.

access cost: The one-time installation charges plus the recurring costs for access to one or more network services, such as Internet access.

add-on charges: Monthly charges beyond access costs. Add-on charges are mandated by the government and administered by the carrier. These types of add-on charges are also referred to as regulatory fees.

analog: A method of representing voice signals through a variation in the amplitude, frequency, or phase of an electrical signal. POTS telephone lines originally used (and in many areas continue to use) analog transmission to gain access to the public telephone network.

application layer: The top layer of the TCP/IP model. The application layer is where a packet is first encoded or last decoded. For the sender, it is the layer at which an application first presents information to the protocols to be packetized. For the receiver, it is the layer at which information is finally depacket-ized and ready for use by the application.

area code: A three-digit code that represents a specific geographic calling area in North America. The area code is dialed first in the sequence of calling any telephone ...