A simple analog telephone line is a voice circuit historically made from copper wire that runs from your local phone company's Central Office (C.O.) building to your business location. The central office houses telephone switching equipment that connects you to the Public Switched Telephone Network (PSTN). This is sometimes referred to as the local loop. Once the analog telephone line is installed, someone can call the phone number that you have subscribed to, and the phone company can connect the call to you.

Good points to remember about analog telephone lines are that

• One phone number is associated with one line
• One line can handle one conversation at a time; when the line is in use, a busy signal is heard

• C.O. Line – Refers to the fact that the line connects you to the Central Office
• Copper Line – Refers to the historical medium that carries analog signals, namely copper
• POTS Line – Plain Old Telephone Service
• Analog Line – Refers to the analog electrical signal used to transmit voice

If you have a small office (1 – 3 phones), each telephone can be connected to the local loop and then receive its' own phone line. However, if your office is growing and you need to connect many phone extensions to the PSTN, it just doesn't make financial sense to pay for separate lines to each phone. In most circumstances every employee does not need to be on the phone at the same time. Instead, by using the trunking concept you can reduce the amount of telephone lines you pay for while servicing every phone in your business. In fact typical business phone systems are configured in ratios of 3-4 telephone lines for every 8 phone extensions.