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#63683 by SecurityTech
Tue Aug 31, 2010 2:44 pm
Voice over Internet Protocol (VOIP) was created as a means to send human voice over the standard Internet based data networks in the world. In its simplest form, VOIP simply digitizes the voice and sends it out in tiny pieces (packets) and then reassembles those pieces and converts the digital voice data back to analog sounds. The challenge with VOIP is that IP packets can get dropped under traffic conditions. For computer data, it’s not a problem because computers can re-send the dropped data packets. For voice data, it’s a problem because the information that’s lost is time critical to reassembling the sounds for the hearer. That’s what is known as dropouts. In addition, the quality of what is digitized is also taken into consideration. Since human speaking is relatively limited in frequency range, not all the audible frequency spectrum is needed to be digitized. Only those frequencies that are prevalent in human speech need be digitized. Latency is another factor which further complicates the task. These factors taken together can limit the ability of a VOIP system from not only performing well for high-fidelity speech but especially for machine communication using older methods such as modems as in fax machines and alarm systems.

Bandwidth is a measure of how much data (usually in megabits today) which can be transmitted in a given unit of time (usually per second). VOIP systems require a steady baseline of bandwidth over time in order to perform effectively. Better quality VOIP systems have typically been implemented with a feature called Quality Of Service (QoS) that assures that time critical voice information packets get prioritized higher than computer data so that VOIP data packets will take precedence and have a better chance of getting to the destination preserving the integrity of the phone call. Ooma has QoS, and this is the backbone of quality that is largely responsible for successful fax and alarm communication over VOIP. VOIP systems perform better over data connections that are both fast in terms of bandwidth and are fairly consistent in terms of bandwidth over time. So, the Internet connection is a fairly critical and fundamental part of ensuring a good VOIP experience. Bandwidth is measured and considered in each direction (from the source to the destination [up] and from the destination back to the source [down]). Ooma generally needs at least 384 Kilobits per second for going up the network and at least that much for down also. When using VOIP, Internet connections always have other data to transmit and receive simultaneously. You therefore need a connection that is reliably faster than the minimum speed needed for VOIP. For example, in Atlanta, DSL Lite is generally 128 Kbps up and 768 Kbps down. That is not ideal for VOIP. Quality will likely suffer resulting in dropouts. Even DSL Standard only provides 256Kbps up and 1.5 Mbps down. So, first make sure your data connection to the Internet is both fast and consistent over time. You can go to various websites to measure your Internet connection performance (for example visit both and

When using the Ooma Telo for machine to machine communication using the phone line, such as fax machines and alarm systems, Ooma recommends using the *99 prefix in front of the phone number and adding a delay code to the phone number if you can. This tells the Telo to use a different method of digitizing the analog signals that’s not limited to voice frequencies and should result in better success rates.

Traditional telephone lines from the phone company enter the home through an interface called a demarcation point or simply demark. When disconnecting service, sometimes the phone company simply stops providing a dial-tone but the wires stay connected to their equipment, and this equipment can still be putting voltage on the phone line. So when switching to any VOIP system (including Ooma and using the Telo or hub) to provide phone service to your home through the existing wiring, it’s imperative that the home telephone wiring be first disconnected from the phone company wiring at the demark. You should have a low voltage technician who is trained on phone systems do this. In addition, alarm systems when properly wired also “capture” the phone line and “return” it at the demark. This practice ensures that alarm system gets exclusive access to the phone line whenever the alarm system needs to transmit something to the central monitoring station. In order to preserve this proper alarm system phone interface, the alarm system must “capture” the phone line from the Telo and “return” it to the house wiring. This is a non-trivial procedure to do correctly and should be done by a trained and experienced alarm technician.

Additionally, for modern alarm systems, we find that the SIA format almost always works more successfully with VOIP than the popular Contact ID format. SIA is equivalent to Contact ID and both are digital data formats designed to transmit more meaningful details from the alarm system to the central monitoring station. Contact ID pre-dates SIA and is therefore more widespread in use. SIA stands for Security Industry Association and is the newer universal standard for alarm communication. You should have an experienced alarm technician program the alarm system to these standards. Do not attempt this yourself because alarm system programming is complex, and one simple mistake can prevent your alarm system from working properly. Remember, no system is perfect. It’s imperative to thoroughly test the alarm system over the new VOIP system repeating the test many times to achieve a statistical significance ascertaining expected reliability (reliability = successful transmissions ÷ total transmissions). Advance Warning Security is presently running an ongoing test every hour to see how Ooma performs at various times and over several days to aggregate statistics. Expected reliability will very likely be less than 100% (even the traditional highly reliable phone company does not have a 100% transmission record). Also remember that VOIP reliability is fundamentally reliant upon the reliability and bandwidth of the Internet connection which varies from time to time. Finally, also remember to put your Ooma Telo and all network equipment on a battery backed up power source so that your VOIP can operate in a power outage. Be sure to simulate a power outage to make sure it will work when you need it. For better alarm reliability, consider a radio backup from Advance Warning Security ( if you are in the Greater Atlanta Georgia USA region.
Last edited by SecurityTech on Tue Sep 07, 2010 6:42 pm, edited 4 times in total.
#63970 by SecurityTech
Mon Sep 06, 2010 6:47 am
Advance Warning Security ( has concluded our alarm testing using the Ooma Telo. We sent a test signal every hour of every day for 1 week configured using the SIA format and using the Ooma Telo *99 command and a pause programmed before the central station phone number. The alarm system was programmed to transmit a maximum of 8 times in case of a communication error. The Internet connection we used was residential grade rated at a maximum of 12Mbps downstream speed and 2 Mbps upstream speed. Our Ooma Telo was configured to use Qos with Upstream set at 1000 and Downstream set at 6000. The voice line was in use sporadically throughout the test. The Internet connection was fairly well used during waking hours. Here are our test results:
16 ADDITIONAL UNDEFINED SIGNALS RECEIVED (likely garbled communication and failed attempts)

9% FAILED FIRST ATTEMPT (undefined signals / total signals)

This means that our central station received all of the test signals that were sent; however, not all the signals were received upon the alarm system's first attempt to transmit. This means that the alarm system had to hang up the phone line and dial again (possibly more than once) to attempt to get the communcation through successfully. This also means that in 9% of the attempts, alarm communication took longer than a single attempt. A typical signal communication attempt takes between 30 and 90 seconds each.

We cannot say whether or not this is acceptable for you. You will have to draw your own conclusions considering that these test results were specific to our Internet connection speed and reliability, our alarm equipment, and a myriad other criteria specific to this test. Your results will likely vary, and you should conduct your own testing. We hope you find these results informative nonetheless. If you are in the Greater Atlanta Georgia USA region, and you need to hire a professional to assist you in setting up your Ooma Telo, you may contact us at
Last edited by SecurityTech on Mon Sep 06, 2010 7:15 am, edited 2 times in total.
#63974 by murphy
Mon Sep 06, 2010 7:32 am
One important point that is easily missed is that SIA format was used.
The common format today is CID.
ADT's proprietary version of Honeywell's Vista 20P only has CID format.
#64012 by SecurityTech
Mon Sep 06, 2010 4:09 pm
We did try CID initially before our test began. But like all other VOIP systems, we were not able to get it working reliably. SIA uses Frequency Shift Keying (FSK) modulation. Honeywell's Vista platform is an older design (formerly Ademco) and does not support the newer SIA standard. CID uses Dual Tone Multi Frequency (DTMF) modulation.
#73943 by markywheels
Sat Jan 29, 2011 10:43 am
Looking at my Demark, I see exactly how the alarm system captures the phone line and returns it. Once I disconnect my house wires at the demark I don't see how the alarm system will be able to capture and return it to the telo. Can you give me more technical details to pass on to my alarm technician?

#73944 by murphy
Sat Jan 29, 2011 10:51 am
Connect the phone port of the Telo to the place that you disconnected your old phone company from. The Telo phone port goes to the input of the alarm system. The alarm system output feeds the rest of the house.

The alarm system must dial *99 pause before it dials the central office phone number.
#74639 by Jack667
Tue Feb 08, 2011 5:51 am
Should I expect similar VOIP performance with my Telo as I was getting with my Comcast VOIP service? I currently have the Comcast cable connected to an EMTA, which has a phone cable (RJ-11) going to a small junction box. Out of that box is a connection to the alarm and another wire to the home telephone wiring. I was planning to take that phone cord from the junction box, and disconnect it from the EMTA and plug it into the Telo.
After reading this, I'm concerned about SIA, *99, and 'capturing' the phone line to the alarm.
Any advice?
#143381 by SecurityTech
Tue Jun 19, 2018 6:30 am
NOTE: Around 2017, Ooma made changes to its VOIP system that made it completely incompatible with traditional alarm communicators. We tried a variety of alarm formats with zero success. No signals from traditional alarm panels that were previously working over Ooma were able to get through anymore. If you have a traditional alarm system that uses a phone line, there may be some options for you. There are dial capture devices that may be useful if your alarm supports a transmission format of SIA or CID. For native Internet transmission, DSC makes a product, TL-300, that uses dial capture to translate alarm signals to a native Internet IP format for transmission to alarm central stations that support IP signaling from the TL-300 device. Uplink and Telguard make dial capture products that send signals over cell networks; popular products are the LTE30EX and TL1EXPRESS respectively. All of these products give you the freedom to stop using a phone-line provider altogether. At Advance Warning Security, we are experts in security systems. If you are in the Atlanta, Georgia region and need installation services and/or alarm monitoring services, please contact us through

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