Traditional telephony has been based on basic business phone service, also called POTS or Plain Old Telephone Service. Old is right. Analog phone lines have been used for over 100 years and are still going strong. They’re highly reliable, deliver clear voice quality and don’t suffer from digital artifacts like latency.
Analog lines were originally intended to be one line per telephone. Key systems allow multiple lines on each phone so you can select which one to answer manually. All the but the smallest call centers have more lines and more agents than a key system can handle. That means using a PBX or Private Branch Exchange to automatically assign lines and direct incoming calls.
What PBX offers is automation. If you only need a half dozen or so outside lines, analog business lines still make economic sense. You connect them to your PBX using FXO (Foreign Exchange Office) ports on interface cards that plug into your PBX system.
When you need more than a half dozen or so outside lines, digital trunk service starts to make sense. Why? It’s because there is a cost advantage to bundling multiple phone lines into one trunk line. You may already have multiple analog lines coming in via a multi-pair binder cable. This is different. A T1 line uses two twisted copper pair to carry 23 or 24 separate phone lines digitally. Yes, those are the same copper pair that would otherwise be used for analog phone service.
The way this works is that the phone conversations are digitized at one end using an analog to digital converter and converted back to analog at the other end using a digital to analog converter. Each call is assigned its own digital timeslot or channel. They are kept separate so that there is no cross-talk between calls. T1 is a synchronous system that has strict timing at both ends of the line. Latency is almost non-existant. However, any unused channels are transmitted empty. All channels are constantly being exchanged between your PBX and your telephone service provider.
Why the choice between 23 and 24 phone conversations on a T1 line? All 24 channels can be used for telephone calls. This is called a T1 telephone line or T1 trunk. The other option is to use 23 channels for conversations and use one channel for switching, signaling and data, such as ANI and Caller ID. That option is called ISDN PRI or T1 PRI. PRI trunks are very popular with call centers because they offer the Caller ID information and faster switching times than normal T1 phone lines. Your PBX system may have multiple PRI ports so that you can have 23, 46, 69 or more outside lines for your call center.
SIP Trunking is an alternative to ISDN PRI. It is based on VoIP technology and uses packets rather than channels. SIP Trunks can be interfaced to older technology PBX systems and the newer IP PBX phone systems. There may be cost advantages for SIP Trunking, especially if using a lower bandwidth CODEC (Coder/Decoder) than the industry standard G.711. Some newer CODECs offer high call quality while transporting more simultaneous calls on the same line bandwidth.
SIP Trunking also opens the opportunity for cloud communications or Hosted PBX. With a hosted system, both the outside lines and the PBX switching system move to the cloud. You have only phones and a VoIP gateway in-house. The advantage to a cloud hosted solution is that you avoid heavy capital investment, pay for service by the agent seat per month, and don’t have to worry about maintenance or upgrades. The service provider takes care of all this for you.
Are you starting up a new call center or contact center, facing an upgrade cycle or expanding operations? If so, this is the perfect time to check business phone service options and prices for call centers and contact centers. You could gain performance advantages at lower prices now.