Trunk Options – An Overiew
By: Chase Christian
When implementing a VoIP system, you have a few choices when it comes to deciding on your voice trunks. Trunks are your connections to the public telephone network, and they’re what allows you to receive inbound calls and make external calls. Your company will need plenty of trunks to ensure that you always have the capacity to make and receive calls.
The most basic type of trunk is the analog trunk, also known as a phone line or POTS line (POTS stands for Plain Old Telephone Service). You are probably familiar with this type of trunk, as this is likely the type of service you have in your home. Analog trunks are simple, you just plug your phone cable into the jack and you’re able to make calls. Unfortunately analog trunks’ simplicity also works against them, as they don’t have the advanced features of the newer trunk types. They’re also usually very old, as they were installed decades ago, and the quality of the analog circuits are not always good. One powerful feature of analog trunks is that they don’t require power to function. Even if the power is out, you can still use an analog trunk, which makes them perfect for backup or emergency phone connections. This feature of analog trunks keeps them relevant even in today’s digital world.
The T1 trunk is a digital trunk, making it much more advanced than an analog trunk. They’re typically found in businesses. T1 circuits can be used for data or voice connections, and we’ll be specifically talking about the voice type of T1s here. A single T1 trunk can handle up to 24 calls at once, making it a great way to get a lot of trunks into your VoIP system. The downside is that a T1 trunk is often overkill for a smaller branch office that doesn’t need as many trunks. One options with VoIP is trunk consolidation, which is where you purchase a T1 at your main site, and then allow your branches to share that T1 by communicating over a VPN network (over the internet).
A PRI trunk is an advanced form of the T1 trunk. A PRI can handle calls faster than a T1, meaning your calls are connected faster when dialing out or getting calls in. You can also do advanced call routing and caller ID features when using a PRI connection. A PRI can only handle 23 calls at once, since it uses the 24th T1 channel for its advanced features. You generally want a PRI instead of a T1 if it is an option at your location. PRIs can also be split into voice and data channels, allowing you to use some of your PRI bandwidth for data (internet) and some of your PRI bandwidth for voice. This makes it ideal for a smaller site, as a single PRI connection can serve both your voice and data needs.
SIP trunks are the newest type of trunks available. They’re completely digital and allow for many advanced features. Unfortunately since SIP is still a relatively new technology in the telephony world, many VoIP systems aren’t fully compatible with SIP trunks. SIP trunks are likely the trunks of the future, but most companies are sticking with a mix of analog and PRI trunks in the meantime. The telephony world doesn’t move very fast, and so there’s little risk of a trunk technology becoming outdated. We are still using decades-old analog trunks, after all.