How Digital Phone Systems Work?

by Jared Paventi

Traditional telephone

Before looking at a digital phone network, it is worth briefly examining an analog network. Analog phones utilize the traditional RJ-45 telephone wiring present in houses and older business buildings. Analog systems convert voice and data noise to electrical impulses and transmit them across wires to a switch. This internal switch controls incoming and outgoing calls for the network, communicating with the outside world over the phone provider's line.

What is a digital phone network?

Comparing analog and digital phones is like comparing a typewriter with a computer, both in capabilities and technology. While analog systems use electrical impulses, digital phone systems compress and convert voice information into a series of zeroes and ones (called binary code). The caller's voice is translated at the phone, set along a digital network and converted at the receiver's phone. Digital phones are connected by Category 5, also known as CAT 5, cable. This is the same networking cable which connects computers to networks. This high-speed cable carries voice information to and from a digital switch, which sends the call out over a broadband internet connection.

How does a digital phone network operate?

A user picks up the phone and hears a dial tone. The person dials a number and connects with their intended caller. While there are no differences on the front end, the back end operation is quite complex. First, the dial tone heard is fake. It's a function of the internal phone network that shows users that the phone is properly functioning. Dial tones are holdovers of the analog phone era and users immediately associate the lack of a dial tone as a malfunctioning phone services. The phone itself is basically a simple computer running a number of functions. When a number is dialed, the computer in the phone navigates from the internal network through its host switch and out to the municipal telephone network to find the intended receiver. When the user speaks into the phone handset, the computer converts the voice to binary code, compresses it for travel and sends it along the connected call. Incoming noise is converted and compressed at the switch and decompressed at the user's phone.

About the Author

Jared Paventi is the communications director for a disease-related nonprofit in the Northeast. He holds a master's degree from Syracuse University's S.I. Newhouse School of Public Communication and a bachelor's degree from St. Bonaventure University. He also writes a food appreciation blog: Al Dente.