Many of you may have a PRI or a T-1 circuit connected to your telephone system as your main source of dial tone. A T-1 has 24 channels (trunks) and a PRI has 23 channels for voice communications. Each channel serves as a single telephone trunk/line and can conduct a call with the outside world; it is the same as having 23 or 24 separate phone lines. Unlike traditional analog (copper) lines, telephone numbers are not assigned to each channel. Going forward we will refer to both types of circuits as a PRI.
What happens if this PRI circuit goes down? You lose your ability to make and receive calls. This can be disastrous to your bottom line because you have the potential to lose money and customers. There are several points of failure; the carrier’s central office, the cabling from the central office to your location, carrier provided equipment and your telephone system. If any of these points fail, callers will hear a ring with no answer or a fast busy. Even worse, they will not reach your office. The worst possible outcome is that the caller is impatient or thinks you are out of business and calls another vendor.
There are some ways to minimize this potential business nightmare.
First, you can install back up telephone lines from a different carrier that are different in form (technology); i.e. copper, FIOS, cable or SIP phone lines. This way if the PRI goes down, you still have alternative dial tone connected and working in your phone system. Once they are connected to your system, you have your PRI carrier program your PRI with direct trunk overflow (DTO). In the event of a PRI failure, all calls made to your main telephone number will automatically be forwarded to the backup lines in the phone system. In this scenario, the number of back up lines connected to the system will limit the number of incoming simultaneous calls.
With DTO, there should be minimal disruption in service. Keep in mind that you may only receive as many calls as the number of backup lines in the system. If the number of incoming calls forwarded exceed the number of backup lines, the callers will hear a busy signal because there are no open lines to reach your telephone system. For example, if you have 4 backup lines in the system, the fifth incoming call cannot reach you phone system and you will not get that call. Typically, we suggest 4 backup lines because circuits are usually not down more than 1 hour. Please keep in mind that some carriers charge a monthly fee for DTO but it is well worth the cost if you want to ensure the continuity of your business.
Another strategy to maximize the number of incoming calls received during a PRI outage is to have Direct Inward Dial (DID) numbers configured on your PRI. In addition to a company’s published main telephone number, a PRI circuit can provide a block of telephone numbers for calling a company. Much like assigning an email address to each employee, each DID serves as a dedicated telephone number assigned to an individual employee. It allows an outside caller to directly reach the employee’s extension without the assistance of an automated attendant or operator. For more information on DIDs, please see this blog. Once employees have assigned DIDs, the PRI carrier can program DTO for all of the DIDs. Upon a PRI failure, each DID is forwarded to the employee’s cell phone. While these calls will not be routed to the phone system, at least they will be answered by the intended recipient or the employee’s cell phone voice mail.
Take note that not all carriers will provide DTO to multiple alternative telephone numbers. If they do, you should find out if there is an additional charge and whether it is automatically effectuated upon a PRI failure. Some carriers that offer this option may provide the service but it will not be automatic; the carrier may require the customer to visit a portal to initiate the call forward for each telephone number (DID).
If you choose not to pay the monthly fee for DTO, you have the option to call the carrier when you realize the PRI is down. However, keep in mind that it may take a bit of time for you to realize the outage and then to reach the carrier to effectuate the call forward (DTO). Some carriers will not commit to implementing the call forward immediately, claiming it takes some time to process the request.
If you already have DTO service on your PRI, we highly recommend a call to your PRI carrier to confirm the telephone number assigned for the DTO upon failure. We know of at least one client that was paying the monthly fee for DTO but the carrier failed to program the call forward telephone number in the DTO service. Unfortunately, this came to light when the PRI failed and they were not receiving the calls on the backup lines installed in the system. It is also imperative to confirm they have the correct telephone number for DTO.
Take into consideration that there are carrier charges for DIDs and in most cases, DTO. In addition, there may also be equipment and/or labor charges from your telecom vendor to connect back up trunks in the system. Please contact your carrier and telecom vendor to discuss these business continuity considerations.