Out of all the technologies we support and deploy, the one that people seem to have the most difficulty understanding is telephony. I’ve always loved phones. My parents took me to Disneyland when I was a toddler, and they made the mistake of letting me wander into an AT&T phone store, where they had the latest 1980s analog phones on display. I cried when they hauled me out of there, kicking and screaming. The idea that you can pick up a telephone, push some buttons, and talk to anyone, anywhere in the world, is still one of the most amazing innovations that mankind has ever come up with.
For a business, the acquisition of a corporate phone system has always been a rite of passage. To have menus, music on hold, voicemail, and an operator transferring calls makes a company seem legitimate, in a way that someone answering “Hello?” on the third ring does not. It used to be really expensive to have a system that can do these things. Not so much anymore.
The ability to park and transfer calls, encode voicemail and send it to email, play music on hold, apply different time conditions and routing throughout the day, and monitor/log call traffic is usually managed with equipment called a PBX, which stands for Public Branch eXchange. According to Wikipedia, this is “a system that connects telephone extensions to the Public Switched Telephone Network and provides internal communication for a business.”
Some PBX equipment is on premise, which is a specialty of ours, and some of it is in the cloud which is a specialty of pretty much everyone these days. There are a few different ways to get dialtone for your business, so the purpose of this article is to go over those.
Analog – Analog isn’t dead yet. This is the easiest form of phone service to understand, because it’s very physical and very literal. A pair of copper wires uses modulated electrical pulses to transmit full duplex voice. Analog is compatible with legacy systems like fax, postage meters, and credit card terminals, and one number corresponds to one pair of wires, which corresponds to one call. Some older PBX systems are entirely analog, and you can actually hear them switching as calls are transferred. Today, it’s more common to use a DADHI adapter or a multichannel Analog Adapter to bring the calls into a computerized PBX. Fun fact: this is sometimes called “POTS” which stands for “plain old telephone service”. Secretly, I think it’s great fun to set up analog lines. It’s sort of like using a typewriter. It feels grand and important in a way that typing on a laptop doesn’t, but it’s comparatively inefficient.
Public BYOB IP Transport – This is what most people mean when they say VOIP. These are calls which are digitized, packetized, and compressed to travel over a data network. To save even more money, the public internet is used for call transport, which means public carriers don’t have to build out infrastructure. There are a number of security and quality issues that this introduces, but those are steadily being mitigated. The biggest issue with using the internet for calls is that those calls are riding on the same network as data, which means video streaming and other high bandwidth activities can disrupt voice calls, which need low latency to work well. Even if you’re not watching Netflix while you’re on the phone, the shared nature of internet infrastructure means that latency anywhere in the route will affect call quality. For this reason, we have been reticent to recommend public “bring your own bandwidth” VOIP services, although they are becoming very popular. Frequently, what people call “VOIP” is really just an analog adapter that is registering to some sort of Cloud PBX, especially in the residential space. However, we can now resell Public SIP trunks which work almost like private ones, but cost less. Another advantage of public voip is that it’s easy to get numbers in non-localized area codes. It’s especially good for small workgroups such as branch offices.
Private IP Transport – This is when a direct connection is created between the PBX and the telephone carrier, and no public bandwidth is used. Although this is still technically “VOIP”, it carries with it none of the same problems as its public cousin, because it’s running on protected private bandwidth. For example, at our office we have a SIP trunk from Cox Communications. Although it’s packetized data, it uses a separate modem from our internet connection, and it’s a direct connection to Cox’s datacenter in Rancho Santa Margarita, where it completes its rendezvous with the public phone network. We can’t use the SIP modem for internet, because it’s not an internet connection. The traffic stays on Cox’s network until it hits publicly switched phone networks, and we can stream as much video as we want without impacting call quality. It’s a better way to do it than BYOB, and it’s better and cheaper than analog. Another trend is carriers offering standalone endpoints with a remote PBX or faux-analog lines on this service model. This is much more profitable for the carrier than SIP trunking, and requires less know-how to set up.
A Word About Channels and DIDs – This is where digital gets a little complicated. There are no “lines.” Since there is no correspondence between a pair of wires, a phone call, and a phone number, you can do some things with digital telephony that are kind of interesting. Think of channels as how many calls you can have going on simultaneously. 8 channels means 8 calls, or 4 calls that are routed to an external number. (Calls can come in on one channel and go out on another – this would happen if you’re forwarding to a cell phone, for example.) DIDs or “direct inward dial” are the phone numbers. You can have one DID and 50 channels, or one channel and 50 DIDs. An average order is something like 8 channels and 50 DIDs, which would mean a company with 45 employees could give everyone a direct number, but only 8 people could be on the phone at the same time.
You can also combine these. For example, one of our customers uses private ip transport for their corporate office, but has a number of public trunks for projects in other parts of the country. Sometimes when analog is taking a while to install, we will set up a prepaid public SIP trunk so that the customer can make outbound calls. There are a lot of creative ways to make the phone ring these days.