The Difference Between Active and Passive Alarm Monitoring

June 21, 2022 | By: mm-admin

Clients often ask us, “How do you send and receive signals in your alarm monitoring station?” Because our monitoring station complies with ULC standards, we employ active and passive forms of communication, acknowledged within the CAN-ULC standard referenced in the Fire Code and the Building Code. By utilizing these recognized forms of communication, FMC can monitor your alarm system in various ways, enabling us to adapt to any possible scenario your site may present. Below we will explain the difference between active and passive fire and security alarm monitoring.

Active Alarm Monitoring

Active alarm monitoring implies that the Signals Receiving Centre (SRC) actively supervises the communication channel between your building and the SRC. The SRC conducts this supervision every 180 seconds. With an acknowledgement between the monitoring transmitter in your building and the monitoring receiver in the SRC. This means that if there is a communication failure between your building and the SRC, our dispatch will be notified about it within 180 seconds. The ULC-S561 standard mandates FMC to notify you of this communication failure if it has not been restored within 5 minutes. If the communication failure persists, FMC will place your system on “manual watch,” requiring someone on site to call 9-1-1 if an alarm is triggered. Systems that utilize active monitoring include:

  • Cellular
  • IP – provided that a 24-hour battery back up is present

Systems that utilize active alarm monitoring are typically very stable, and have very little service downtime.

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Passive Alarm Monitoring

Passive alarm monitoring is simply less regular supervision of the communication channel between your building and the SRC. In a passive monitoring scenario, the system performs the check-in once daily at a predetermined time. Forms of passive monitoring can include:

  • Phone line
  • Cellular
  • IP

If this sounds like a less secure option than active alarm monitoring, you’re correct. A passive system that receives an acknowledgment and then encounters a disruption would not identify the issue until it misses its next scheduled check-in. Testing times can be daily, weekly, or sometimes even monthly.

In passive monitoring scenarios where fire or security alarm monitoring require (or desire) higher-level security, dual path monitoring is required. CAN/ULC-S561 states that when passive forms of communication are used, two non-redundant forms of communication need to be present. In this set up, each line of communication monitors each other. This way, if one goes down, the other advises the monitoring station and confirms its activity. In a scenario where a phone line disruption occurs, and cellular communication serves as the second path, the cellular line would transmit a signal to the monitoring station indicating the absence of the phone line. The cellular line could still transmit signals from that building, and vice versa if the cellular channel went offline.

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