Types of Line Service for Phone Systems

A Brief Explanation of the Different Types of “Lines” a Telephone System can Utilize

With over 35 years in the telecom industry from our foundation here in Tampa, Fl. CSM has seen the titanic changes in the way that voice is delivered to a business. There was a time when an actual human operated a switchboard, sending callers to the correct destination. Then, machines were invented to do that automatically. However, the basic concept of voice travelling over copper wire, stayed static. Now, of course, voice is merged seamlessly with data, and instead of vibrating a wire, is sent via data packets and then reassembled by your telephone system, VoIP.  So what options are available to businesses and other organizations in today’s fast changing marketplace? Simply, there are the two traditional choices of copper lines, or CO (Central Office, the old GTE/ Bell/ Verizon/ etc) and T-1/ PRI; and then VoIP, or SIP (Session Initiated Protocol).  Let’s take a closer look at these three choices and how they impact the operations in an organization.

Copper (CO)

CO trunks are the most traditional of the telephone line service available in today’s marketplace, and also the least likely to have any problems. However, they can also be the most costly due to several factors.

  • How does it work?
    • Copper lines deliver the most traditional service possible to the telephone system. They are the typical, Line 1, Line 2, Line 3, etc. When a call is coming in, the user answers the ringing line, places it on hold, etc. When a call is active on a line, then that line is busy and i use, so new calls roll over to subsequent lines. All calls must be routed through a answering position such as a reception or automatically through an automated attendant menu.
  • How is the reliability?
    • Not surprisingly, old fashioned copper CO lines are the most reliable of the different line service options in today’s marketplace. Due to the fact that the infrastructure has been in place literally for decades, it is also readily available at nearly every location in the United States, whether rural or urban.
  • But what about cost? $$$
    • Copper CO lines are actually the most expensive option that a business can use, due to the nature that each line is billed as a separate item.  If a business wants “roll over” feature, or “hunt group, ” that is additional to the base charge. There are also many other additional feature fees such as these. Long distance is also typically far more expensive than what is charged on T-1/ PRI or SIP service; not only calls outside a user’s area code, but also calls within that code but in a different “rate center.” Finally, each item is taxed separately, adding significant cost per line. The average rule of thumb is that each CO line costs about $45 per month. Of course, this varies by promotions that may be offered by carriers or bundles, however it is a safe number to use for budgetary or comparative purposes.

T-1/ PRI

Digital trunks, primarily known as T-1 or PRI, have been around for a long time now. Gaining popularity in the mid- 1990’s, a full PRI consists of 24 channels of voice, 23 used for service and 1 utilized as a “D” channel for communication back to the carrier.

  • How does it work?
    • With a PRI/ T-1, lines do not come into the telephone system like copper CO trunks, instead, they come into the business as a single digital trunk, consisting of “channels” where the voice traffic moves across. So, when that call comes into the phone system, it can be programmed to go wherever we like- to an answering position, to an auto attendant, to a voice mail box, or to a specific telephone or user. Telephones typically have “Call” buttons, sometimes labelled as “Loop,” which are specific to that user individually. When a client needs to be placed on hold, the user instead “parks” the call onto a park button, park zone, or a specific telephone- the exact procedure for the function depends on the specific type of telephone system being used.
  • How is the reliability?
    • Service issues with T-1/ PRI are not common, however they are far from unknown. Typically, it is due to major outages in a data center where the equipment originates, but it can also be due to loose wires at the customer site. Issues seem to cluster geographically and happen in spurts. We have had customers with recurring issues for months- and then nothing for years. Typical service outages last for an hour or so, but if due to infrastructure, may last for a day or more; this however is rare.
  • But what does it cost? $$$
    • A T-1/ PRI is surprisingly affordable, given the amount of service that is provided by the product. Part of our business here at CSM, in addition to providing new phone systems and also service, of course, is coordinating the line service. We have seen T-1/ PRI for as little as $350 per month, to up to $800 per month. The price varies by location, available carriers, and active promotions. A safe budgetary figure would be $500 and an additional 15% for taxes. Considering that this provides up to 23 channels of communication, it is quite a bargain compared to traditional copper CO lines.

SIP Trunks

Finally, we come to possibly the hottest topic in telecom today, SIP. This protocol is so much more than just voice, but we will limit our exploration on the subject at that part. SIP, or Session Initiated Protocol, is a form of Voice over IP, VoIP, that has largely overtaken the other main protocol, MGCP. Quite simply, it is using your internet connection to deliver phone service.

  • How does it work?
    • Sip trunks act like a cross between CO and PRI lines. They require licensing on premise based VoIP telephone systems, but are generally included in every phone with cloud based telephones. They can be setup “square key” and operate like a CO line. Alternatively, they can be made to operate like a T-1 with “call” buttons. They also offer the ability to have direct lines, like a T-1/ PRI. Additionally, they typically do not ring “busy” on incoming lines and are not using roll over features like CO lines do. Instead, the carrier provides a number of call paths that all have the same number, or any amount of numbers, associated with them, like a PRI. Simply put, they are flexible and from a programming standpoint, superior to CO or T-1.
  • How is the reliability?
    • This is probably the biggest drawback to SIP trunks. Because they rely on a businesses internet connection, they are dependent on that for service. If you have a slow or poor connection, you can bet that the voice quality will be unacceptable. Additionally, if the SIP trunk is setup incorrectly, such as not including an SD WAN when it really should have it, then quality can degrade very fast. Basically, SIP trunks CAN be reliable and have excellent sounding voice quality, however, they MUST be setup properly and allowed to have “breathing room” on the data circuit.
  • But what is the cost? $$$
    • Cost is one of the major factors in businesses moving telecom to the cloud, or at least to a premise based VoIP telephone system. SIP trunks are a little different than copper CO or PRI in that the taxing mechanisms vary and the costs are not uniform. The cheapest SIP trunk would be a metered trunk with a predetermined amount of call minutes which would include long distance and local calling. These run around $15 per month.  An all inclusive line would be in the neighborhood of $25 per month.

So which type of service is right for your telephone system? Factors include the age of your system, the equipment already on it (or available for purchase/ expansion) and the service offered in your area. Most telephone systems, new or old, can accept CO and T-1/ PRI either with their existing hardware or with adding to the current system. For SIP trunks, if your phone system is less than 10 years old, there is a fairly good chance it can utilize SIP trunks- though this is by no means guaranteed. For instance, Nortel telephone systems could use them, but as Nortel went out of business in 2008, the licenses are no longer readily available. ShoreTel, Avaya, and Mitel can usually take them, but may require licencing or software updates. Further, the geographic location of a business often determines what type of phone service is available. CSM has vast experience with all types of telephone line service, so please contact us for more information and assistance with navigating this sometimes complicated topic.

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