November 2, 2021
By Allan Sanedrin, principal engineer, Fire and Life Safety Signaling Systems
Years ago, public switched telephone networks (PSTN) or plain old telephone service (POTS) were the prevalent means of communicating fire alarm signals from a protected premise to a central supervising station. These traditional telephone networks used a digital alarm communicator transmitter (DACT) to send signals to a digital alarm communicator receiver (DACR) at a central monitoring station.
As PSTN/POTS are rapidly being replaced with cellular and Ethernet/IP networks, it’s common to upgrade a typical fire alarm system by attaching a dialer capture module to the DACT to convert from traditional telephone networks to cellular or Ethernet/IP. Dialer capture modules have many names, such as cellular/IP modules or transmitters, wireless transmitters and digital communicators.
Unlike the transmitters owned by telephone companies, dialer capture modules convert the technology from PSTN to cellular or Ethernet/IP. In essence, this changes the equipment operation requirements applying to the system described in UL 864, Standard for Safety of Control Units and Accessories for Fire Alarm Systems, and NFPA 72, National Fire Alarm and Signaling Code, from DACT to performance-based signaling. The conversion may also change the wiring requirements from loop start required by NFPA 72 for DACTs, to ground start telephone circuits. As such, the off-premises transmission means are no longer considered DACT.
Code officials and other interested stakeholders have asked about the difference between certified dialer capture modules and the more generic (also referred to asd “off-the-shelf”) and often used converter products.
In the performance-based signaling approach, dialer capture modules are unique devices with their own dedicated evaluation and performance testing requirements found in UL 864 for system certification.
The key aspects of testing and certification to UL 864 include:
- Verifying the dialer capture module operates according to the requirements for performance-based technology. These operation requirements differ from DACT operations, so simply converting the communication device does not automatically comply with the performance-based technology operation requirements. One specific requirement that differs is the frequency of check-ins required by NFPA 72 and UL 864.
- Verifying that a local trouble signal is annunciated at the protected premises when a transmission fails to complete.
- Conducting a UL 864 construction review of the suitability of a conduit connection. The connection between the DACT and the dialer capture module is subject to the supervision of open, short and ground faults or limitation to installation within the same enclosure or 20 ft in conduit.
- Verifying that DACTs claims for compatibility of all alarm signaling protocols with specific DACRs, by manufacturer and model. Similarly, with specific DACR equipment in place, claims for compatibility between the DACT and the dialer capture module and between the dialer capture module and the receiving unit must also be verified.
- Verifying that a fire alarm system, including the dialer capture module, has standby power.
- Evaluating that any dialer capture module functions other than those for fire alarm signaling and connections to non-fire alarm equipment do not impair fire alarm signaling. To determine this, evaluate the operation of all these types of functions and circuits to determine that their processes and any open, short and ground faults on the wiring have no impact on fire alarm signaling.
As with the other fire alarm equipment in a system, evaluation of a dialer capture module to UL 864 involves performance and reliability testing, review of installation instructions including programming instructions, construction and product markings and assessment and testing to safety requirements.
The dialer capture module is specifically designed to satisfy the UL 864 and NFPA 72 requirements for performance-based technology. You cannot simply replace the module with any non-specific, off-the-shelf product. Dialer capture module certification to UL 864 is necessary to verify compliance with NFPA 72 and ensure the system will deliver the level of safety, reliability and performance required for a life safety system.
UL certified devices are listed on UL Product iQ™. UL Product iQ is complimentary to use but does require a simple, one-time registration.
Dialer capture modules will be found in the System Control Units (UOJZ) category as fire alarm control unit subassemblies when installed within in a certified fire alarm control unit or DACT, or in the System Control Unit Accessories (UOXX) category when they are stand-alone products interconnected with a fire alarm control unit or DACT.
The specific System Control Unit Accessories referenced in a fire alarm control unit’s installation instructions are necessary equipment for central station, remote station or proprietary services performance-based technology signaling.