you may not always have the very latest software release and system capabilities. Be- fore the local telephone company invests in upgrading the central office switch, there needs to be sufficient demand to justify the expense of the upgrade. Since the local telephone companies are The Telecom Handbook 58 229 OUTSIDE LINES regulated, they must also apply to the public utilities commis- sion in their state for permission to offer a new system capability as a new service. "The Network" Any group of circuits and their associated hardware is called a network. There are many different types of networks. A single site with a variety of lines connecting it to the outside world may be referred to as a network. More commonly, network is used to describe multiple sites linked together via telecommuni- cations circuits. ISDN stands for Integrated Services Digital Network. This is a collection of standards and protocols for digital communica- tions. The benefit of ISDN service is that it provides more advanced capability over the same pair of wires used to deliver a regular dial tone line to your home or business. Madeline Bodin, writing for TELECONNECT magazine does a good job of explaining the two things that ISDN lines enable you to do which your POTS lines (plain old telephone service) do not. First, ISDN lets you transmit more information from one point to another. It gives you more bandwidth. Comparing the infor- mation being sent on the telephone line to water, a regular telephone line would be like a drinking straw and an ISDN line would be like a 4 inch diameter plumbing pipe. Second, ISDN lets you control the information going across the line from outside the pipe, called out of band signaling. By doing this, more information about each call is delivered, the information is more secure and a number of limitations are re- moved. (Note: Currently, long distance companies accomplish this out of band signaling over a separate dedicated network called Signaling System 7 in order to open and close switches and route calls