Glenn Stok has over 30 years experience developing and supporting automated phone systems. He has a Master's Degree in Computer Science.
Have you ever wondered how large companies can receive so many simultaneous telephone calls without getting a busy signal?
Home telephones and mobile phones provide Call Waiting. You’re familiar with that. But Call Waiting won't work with phone systems. If you want a phone system, such as an automated attendant PBX, to handle multiple callers, you need multiple phone lines with rollover.
Telephone line rollover is the method used to allow more than one caller to get through by routing each caller through the next available phone line.
It's important to understand that rollover is not a function of your in-house phone equipment. Your phone service provider must do it. You need to ask the phone company to roll the additional callers over to the next higher line. That is also known as a hunt group.
All your callers will dial your main number, but if the first line is in use, the next caller rings in on the next unused line. If all lines are in use, then the next caller will get a busy signal.
On the other hand, call waiting will allow a second caller to be answered on a single line. This is no good for a phone system, which is designed to route each simultaneous caller to a particular department or personnel.
A phone system will answer any phone lines that are ringing. If your phone service provider does not roll busy lines over to the next line, then there is no way that the phone system can answer those additional callers.
How Many Lines Do You Need?
Simple answer: One line for each caller. So if you need to handle, say, ten simultaneous callers, you need ten lines from your phone carrier.
You still use just one phone number. The additional lines do have their own numbers and can be dialed directly. But the main idea is that the first number is the only one necessary. If the line is in use, the caller rolls over to the next line that’s free.
In other words, the first caller rings through on the first physical line, and the next caller "rolls over" to the next physical line that is available. This rollover continues until all lines are used.
If all the lines are in use, then the next caller will get a busy signal. So if you want to support a high call volume for your business, you need to get additional lines from your phone company and request these lines to be configured with rollover to the next line in the group.
The rollover service is usually provided at no extra charge. The phone company profits from the additional line charges anyway.
Why Call-Waiting Is Not Necessary
Keep in mind that the phone system is automated to route the incoming calls.
If you have Call Waiting on any of your lines, the next caller will NOT roll over to the next line. They will be stuck there waiting for the person on that line to respond to the call waiting tone.
That works just fine for a single line, such as a home phone or cellphone. But when you use rollover to additional lines, call waiting will interfere with its operation.
How Does a PBX Phone System Work With Rollover?
All incoming lines organized in a rollover hunt group are connected to the phone system (PBX), and all in-house phones are connected to its extension jacks.
The first caller will ring through on the first line. The next caller will come through on the second line, and so forth.
It makes no difference which line a caller comes in on. The PBX will handle all callers the same way. If the system includes an automated attendant, it will help guide the caller to their desired destination by providing a menu of options.
There are two methods to achieve the same results.
- Each phone is assigned an in-house extension number. All callers dial the same main number, select options from the automated attendant to ring the desired extension or dial a known extension number if the phone system provides that option.
- Each phone can have a direct-dial number. Usually, the last four digits of the phone number represent the extension. The phone system will detect the last four digits and automatically route the caller to that extension.
Note that in the second case, you don't need an individual line for each number. You just need enough lines to support the maximum number of callers expected at the worst load times.
How Does Calling Out Work With Multiple Lines?
Calling out works differently with various models of PBX’s. When any in-house personnel picks up an extension, most phone systems require the caller to press 9 for an outside line. The system will provide dial tone from one of the available outside lines.
Some PBX’s will automatically give dial tone from any available outside line without dialing 9, so calls can be made without pressing any other keys.
To Sum Up, All Things Considered
If you are the one responsible for setting up the phone system, there are things to consider.
Do you know how you will handle all your callers simultaneously? Do you have enough personnel to answer all the calls? If not, then why not just have one line and let the overflow go to voice mail provided by your phone company.
Have you decided on how you'll route all the calls? Of course, you can simply have a telephone connected to each line. But then you have no way of transferring the calls from one to another. You also don't have a smooth transition to route callers to personnel or departments.
That is where the PBX phone system becomes so important. A simple phone system allows a live receptionist to answer all the incoming calls and transfer them to the proper locations.
An automated attendant phone system is the next step up, especially if you don't have a full-time receptionist to answer all the calls. That lets you provide a welcome greeting to all your callers and a menu of options they can select to route to the desired personnel or departments.
A complete phone system should also include voice mail for each extension that will play a personal greeting for each of the personnel and take messages for unanswered calls.
Now you know what’s behind a well-equipped front end for companies with lots of callers.
© 2015 Glenn Stok
Glenn Stok (author) from Long Island, NY on November 05, 2017:
Siva - You need multiple lines in order to have rollover to receive multiple simultaneous calls. The only way you can do that with a cell phone is to use a hosted virtual automated attendant service. Check out this one:
siva on November 05, 2017:
An option for mobile line .., how to make automated attendant + mutli user calling .,, or make it hunting line?
Glenn Stok (author) from Long Island, NY on August 22, 2015:
mgt28 - A lot of my customers always ask about this. They can't understand that having a multi-line phone system is not the only thing needed to receive multiple calls simultaneously. I find myself explaining that they need additional phone lines over and over again. Thanks for commenting.
mgt28 on August 21, 2015:
This is well written. I did Telecommunications 20 years ago as part of my electrical engineering degree. I could not explain this without writing silly equations unnecessary technical jargon.