It seems like just yesterday when I was coming across statements like, “Dealers should advise their customers that changes to their phone service (including digital services, call waiting, auto dialback, etc.) could require changes to their alarm system configuration or programming. Central stations should send periodic test signals to their accounts to ensure that the connection is working.” Actually, these were recommendations from back in the late 1990s by the Security Industry Association (SIA) Telco Compatibility Working Group DC-06.
I can remember as an alarm dealer the introduction of Digital Subscriber Line (DSL) back in the 1980s, when many dealers had to wrestle with often-awkward phone-line splitter and filter combinations. The highly hyped new digital phone technology was often installed at the request of the customer by inexperienced third-party contractors and without notification provided to the alarm service company. Sound familiar? I guess some of us old-timers can say, “Been there, done it, and have the shirt.”
Now that I’ve gotten my monthly alarm war story out of the way, I want to continue by focusing on some of the alarm industry communication formats and standards with which dealers, integrators and security directors have to deal. This is especially true in the rapidly emerging Internet protocol (IP) world and, in particular, voice over Internet protocol (VoIP) phone services.
Still a Need to Know Older Formats
I have noticed an increasing technology skills gap in newer techs entering the industry. These folks are often very savvy as to IP and network connections, but lack knowledge of evolutionary communication formats such as: Ademco Contact ID, express 4-1, 4-2; Acron 3-8 or 4-8 DTMF; Sur-Gard DTMF 4-1, 4-2, 4-3 and 4-3 with Checksum; Franklin/Ademco/Radionics 3-1, 3-1 extended, 4-1 and 4-2 at 10/14/20/40 baud and 40 baud with Checksum; Super Fast Ademco or High Speed DTMF 4-8-1; FBI Super Fast; and Modem II; BFSK, just to name a few.
Additionally, one must remember that even though we would like to move new IP technology along as quickly as possible, the vast majority of today’s alarm communications is still conducted on what appear to be plain old telephone systems (POTS). I carefully state, “appear to be,” since the majority of phone-switching circuit head-ends are now high speed digital. However, on a positive technical note, recent studies indicate users of residential VoIP service will reach 267 million worldwide by 2012.
There are four alarm equipment communication format groups in use today. The first three categories are used in phone communications with alarm panels: Pulse (4/1, 3/1, 4/2, 3/1 with parity, 3/1 extended, 4/1 extended, etc.); DTMF or Dual-Tone Multi-Frequency (Contact ID, Ademco and FBI Superfast, etc); and FSK or Frequency-Shift Keying (SIA, Modem II, IIIa2, BFSK, ITI, Westec, etc.). The last category is IP with two formats: UDP (unpacketed) or User Datagram Protocol and TCP (packeted) or Transmission Control Protocol.
Pulse, DTMF, FSK Formats Detailed
The goal of alarm communications has always been to get data delivered as quickly, inexpensively and accurately as possible. Though this sounds simple enough, it has always been a challenge since the data must travel through not-so-perfect phone systems. The important thing here is to have a good basic understanding of the different technology formats and know which one is best suited for the alarm reporting application.
The Pulse format consists of digits that are transmitted by turning a carrier on and off in a 50-percent duty cycle. Rates and frequencies can vary. This method was introduced very early on and has been considered a very robust format that works very well with noisy and poor quality phone circuits. This method of communication comes with a beginning “handshake” and an ending “kiss-off” signaling sequence.
For example, the amount of data in a Pulse 4/2 signal would have four digits for the account number and only two digits to identify a zone alarm or trouble. Ironically, the Pulse format has been making a bit of a comeback as it has been suggested by some as an alternative method in sending alarm signals over VoIP circuits that are having difficulty with the higher speed DTMF formats such as Contact ID.
The next format group is the SIA DTMF. In these signals, digits are transmitted by turning standard DTMF tones on and off at a specific rate, again in a 50-percent duty cycle. Handshake and kiss-off signals are tones as well. This transmission is faster, has more detailed information and is more accurate with error checking. Flavors of this format might include a four-digit subscriber ID and nine digits, which can include items like a three-digit event code and a two-digit zone code.
With a larger number of digits in the event code, systems can have hundreds of specific events identified, such as 380 for zone trouble or 309 for low battery. Digits are also used for checksum or error checking for data accuracy. This is also accomplished with double transmissions and checking the digits for errors. Ironically, faster and more modern DTMF switching, such as Contact ID, has created some problems with trying to communicate accurately over VoIP network circuits.
FSK transmission formats create digits by shifting a continuous carrier up and down from a base frequency. It is a form of frequency modulation. The phone company uses various techniques to improve bandwidth and voice quality. Some of these techniques are echo canceling, suppression and voice compression. Format techniques such as FSK and DTMF can be affected by these enhancements.
Considerable converting of digital to analog and vice versa are done today. The more audio signals are converted from analog to digital, the closer the signal-to-noise ratio (SNR) gap closes. This causes problems for FSK and DTMF. The Pulse format is not as affected by the noise on phone lines. However, it is slower.
What VoIP Adds to the Mix
Now comes along VoIP technology, which uses broadband technology that covers a wide range of frequencies sent over a network. VoIP uses a certain compression technology or “codec” that can have difficulty with Contact ID transmission. Several troubleshooting areas might be tried, such as switching to a slower Pulse format or adjusting the compression of the VoIP router.
Dealers should be aware they might encounter remote panel uploading/downloading problems as well. Something as simple as the customer being on the Web at the same time an alarm is trying to get through may not work. The truly best options are to upgrade the customer to either a device that will take a panel’s alarm-reporting output and convert it to VoIP or a new panel with IP capability.
