here is a good summary of Cellular backup for alarm monitoring copied from
http://www.emergency24.com/pr/Spring2004.htm.
Commercial and residential alarm systems have a similar point of vulnerability…the phone line. Since most alarm installations rely on basic commercial and residential phone service, interruption resulting from poor weather conditions or deliberately cut lines can leave even the most high-tech alarm system isolated and unable to relay alarm signals. Fortunately, the past few years have seen wireless technologies become more reliable and user-friendly, and they can now be used in conjunction with existing digital dialers to add an extra level of security. The options in wireless alarm devices for installers and subscribers are growing. There are differing technologies that wireless alarm systems utilize.
The three most widely used are Radio, Cellular and Mobitex:
RADIO SOLUTIONS:
Radio units use long-range radio waves to relay signals through towers or relay nodes. AlarmNet, one of the industry leaders in radio alarm devices, provides two types of long-range radio devices; one-way and two-way. These types differ in how they “speak†over the radio network. One-way means that when the device sends a signal, it travels from tower to tower in one direction until it reaches a main node. Two-way radios can communicate back and forth across the radio network, and the units are “polled†to assess whether the unit has not dropped from the network. One-way radios are not polled, but they are capable of sending regular network signals to assure constant connectivity.
CELLULAR SOLUTIONS:
There are two types of cellular technologies; analog/voice cellular and control channel cellular. Analog/voice cellular uses the existing cellular infrastructure to make a phone call and deliver an analog alarm signal (similar to digital dialers) using cellular towers instead of phone lines. The second and more widely used type is control channel cellular. This technology uses digital channels within a cellular scope not used for voice, but which control and initiate the cellular call. This technology reduces interference and distortion when delivering a signal. When looking at the control channel cellular devices, there are four names to consider:
AlarmNet - Produced by Ademco, the AlarmNet-C devices come in different models with varying features. AlarmNet-C is sometimes referred to as Microburst, and it is actually the classification of the transmission type the units use over the control channels. The formats available to send via the AlarmNet-C are Ademco High-Speed and Contact ID.
Telguard is another wireless option that uses Microburst transmissions over cellular control channels. There are various models and classifications, and it is capable of multiple formats, including 3/1, 4/2, Contact ID and Modem IIe/IIIa. Telguards also work with most major central station receivers, which means that you can use a standard digital account number as long as you know which format you would like to send.
Uplink - Produced by Numerex, Uplink also uses the cellular control channel to transmit alarm signals, but it transmits using Cellemetry as opposed to Microburst. Both of Uplink’s current models are capable of sending 3/1, 4/2, Contact ID, Modem IIe/IIIa and Security Industry Association (SIA). Like Telguard, Uplink can be used with any central station receiver that accepts the format you choose to send.
SkyRoute - Produced by DSC (Digital Security Controls), SkyRoute provides cellular control channel alarm signals via Cellemetry. SkyRoute has standalone models as well as snap-in modules that work with existing DSC panels. All are capable of relaying signals in Contact ID and SIA. Within the continental United States, the SkyRoute service itself is operated by Connect24 Data Communications.
MOBITEX SOLUTIONS:
Mobitex is not a new technology, but thanks to increased use and publicity, companies are turning toward this technology and network for new wireless business solutions. AlarmNet has been using this technology for years with the AlarmNet-M service. This very reliable wireless alarm system uses existing communication towers to relay alarm signals. It is capable of giving solid security with supervision communication every five minutes, which in turn gives it one of the best Underwriters Laboratories (UL) ratings.
How do you decide which wireless solution is best for you?
Whether you are in an urban or rural setting, when deciding the appropriate wireless solution for your subscriber, consider signal strength for both radio and cellular coverage, the level of security and supervision desired, the format you would prefer to use and any UL requirements for the installation. As always, you will want to contact the manufacturer to make sure any wireless device you use meets the UL requirements for the subscriber business type, insurance and local municipality.
but in an emergency...
