Alarm Basics, Part 4

May 1999


Alarm Basics, Part 4

The security of the line that carries your store's alarm signal to your alarm company is the linchpin of the whole system


The transmission of alarm signals is perhaps the most complicated, least understood component of burglar alarm systems. Sophisticated electronic surveillance is worthless if your system fails to inform the proper parties of an intruder.

While some jewelers in less-populated areas may use security systems that trigger a bell heard only inside or immediately outside the store, many use systems that also transmit signals to a monitoring facility, such as a police department or UL central station.

Following is an overview of the alarm transmission methods UL recognizes. You may find this information helpful when speaking with your alarm company representative or insurance agent.

Signaling systems
UL certifies seven alarm signal transmission methods. The following methods send signals over regular telephone lines: direct wire, McCulloh transmitter, multiplex, digital alarm communicator and derived channel. Alarm signals also can be transmitted by radio waves or cellular telephone. Some security systems use two transmission methods to reduce the chance of a burglar interrupting the alarm signal.

Here is a brief description of each transmission method (the first three also should have separate line security to achieve maximum results - see box).

  1. Direct wire. A separate, dedicated telephone wire connects the protected premises with the monitoring facility. Its sole purpose is to carry the alarm signal. If you use a direct wire system, be sure it includes line security. Otherwise, a skilled technician can defeat it by approximating existing signals or substituting his own electrical signals. This method may be sufficient for jewelry stores in non-urban areas.
  2. McCulloh transmitter. Though not in widespread use, this method uses a "party line" that connects several businesses to a monitoring facility. When an alarm signal is received via the dedicated party line, the monitoring facility checks a code to identify which business was compromised. Unfortunately, this system can be compromised easily.
  3. Multiplex. This system also operates like a "party line," using one dedicated telephone line to connect several businesses to a monitoring facility. But the multiplex system is not compromised as easily as the McCulloh.
  4. Derived local channel system. This system, which inherently provides line security because of the way it operates, uses the regular telephone company network and a dedicated telephone line to carry signals. This arrangement provides continuous supervision of the communication channel without interfering with normal telephone use. If the telephone line is cut, an alarm signal is transmitted to a monitoring facility.
  5. Radio system. This security system transmits status signals via radio wave to a receiving antenna, which relays the signal to the monitoring facility. In a two-way radio system, the monitoring facility can receive the alarm system's status signal as well as send a signal to ask for the status or confirm an alarm condition, thus, providing line security. One-way radio does not provide line security and is used less often for jewelry operations.
  6. Digital alarm communicator transmitter. The alarm signal is transmitted over the business's regular telephone lines (rather than over a dedicated line), which transmit them to the monitoring facility. An intruder can compromise this system easily by cutting the line. This is the most basic transmission method, but it may be enough for stores in non-urban areas.
  7. Cellular alarm transmission system. This system uses low-power cellular telephone transmission to send a signal from the alarm system to the telephone company network. This can be an effective transmission method in some parts of the country. While occasionally used for primary transmission, it's more often a backup to transmission by telephone lines.

There is no "right" choice for alarm transmission. To select the best method for you, consider a variety of factors:

  1. The transmission methods available from alarm companies in your area.
  2. Your insurer's recommendations and requirements. Will one method reduce your premium more than another?
  3. Your physical and procedural security.
  4. Your inventory and crime in your area.

David Sexton leads the large accounts underwriting department at Jewelers Mutual Insurance Co., Neenah, WI. He also is a corporate member of UL's Burglary Protection Council and the Central Station Alarm Association.

  Line Security

Many alarm systems incorporate line security to supervise the communication channel, which transmits signals between your store and the UL central station or remote monitoring facility. The line is supervised to detect a burglar's attempt to compromise the signal and enter your store undetected.

The more advanced level of line security works on an "interrogate and response" concept. The central station computer interrogates (sends a message that asks what's happening). The alarm system at the store responds with an appropriate message, such as:

  1. System is armed; everything is fine.
  2. System is not armed.
  3. System is armed and something is wrong.

If the central station does not receive a response, it interprets that as an alarm condition.

There are two levels of line security: standard and encrypted. With encryption, the signal is "scrambled" and a decoder is needed to read the signal. The level of encryption available from alarm companies has yet to be tested by independent third parties such as Underwriters Laboratories. But encryption offers promise for the future.

Line security is available for direct wire, McCulloh and multiplex signaling systems. Your insurance agent or an insurance company specializing in

jewelers block insurance coverage can help you evaluate the alternatives and select the most cost-effective method.

– D.S.

Copyright © 1999 by Bond Communications.


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