Digital Alarm Communicator Transmitter (DACT) Fire Alarm Tutorial

When it comes to the subcomponents embedded within fire alarm systems, one critical piece often goes unnoticed until it malfunctions. It's your Digital Alarm Communicator Transmitter, or DACT.

This device may not be the first thing you think about in your fire panel (FACP/FACU), but its role is essential. Serving as a digital bridge, it plays a crucial role in transmitting critical signals. These signals travel from your fire alarm control unit to the necessary emergency personnel or monitoring service.

Today, let's dive into the functionality of the DACT, its application, and how it aligns with the stringent guidelines of NFPA 72. That's the "National Fire Alarm and Signaling Code", which is the benchmark for fire alarm system requirements.

What is a DACT?

"26.6.4.1* Digital Alarm Communicator Transmitter (DACT) Used as a Signaling Interface."

This quote from NFPA 72 may seem cryptic at first glance, but it's a high-level description of the fundamental purpose of a DACT. It's simply a device that sends out a digital distress signal from your fire alarm system to a monitoring station.

It's a communicator that ensures that the signal of a fire alarm does not just echo within the walls of your facility but reaches dispatchers and/or first responders immediately.

Application of a DACT in Fire Alarm Communication

When it comes to the DACT’s specific applications, NFPA 72 states:
"26.6.4.1.1 The requirements of 26.6.4.2 shall not apply when a DACT is used as a signaling interface from a fire alarm control unit to another listed communications means."

This means that the detailed requirements for DACTs can be set aside under certain conditions, specifically when the DACT is connected with an alternative communication system. When not connected to an alternative system, a fire alarm DACT has requirements to meet, such as:

• Using telephone lines.
• Having an additional transmission method.
• Being reliable and redundant.

The referenced section 26.6.4.2 describes requirements for phone/POTS dialing on a traditional copper phone network.

As telecommunications have evolved, the code has necessarily adapted to allow other types of communication networks like radio or the internet. The above code section allows for the elimination of a traditional dialer when using a DACT with a newer communication channel.

Complying with Communication Requirements

The compatibility of the DACT with your chosen communication channel is non-negotiable.
"26.6.4.1.2 The listed communications means shall meet the requirements of either 26.6.3 or 26.6.5."

This clause ensures that the DACT works in tandem with pre-approved and tested communication methods. For a building manager or a system installer, you must select components that are recognized by NFPA standards to work seamlessly with each other.

DACT-Specific Connection Requirements

"26.6.4.2.1* Managed Facilities-Based Voice Network" spells out the need for a DACT to be linked to a controlled voice network.

This means that the DACT needs to be connected to a voice data-capable system, which is separate from regular phone systems. It functions as a dedicated line, ensuring uninterrupted transmission of alarm signals.

Your Control of Communication Lines

NFPA 72 mandates that:
"26.6.4.2.1.1 The connections to a managed facilities-based voice network shall be under the control of the subscriber..."

This places the power directly in the hands of the system's owner. Since you're reading this, that's probably you.

You, as the subscriber, must have direct control over these connections, ensuring that they are not tampered with and remain secure. That's an essential factor in the reliability of fire alarm signaling.

Ensuring Correct Connection Types

On the technical side, ensuring the right type of telephone circuit is vital.
"26.6.4.2.1.2 Special attention shall be required to ensure that this connection is made only to a loop start telephone circuit..."

In simple terms, the code specifies the technical requirements for the type of phone circuit to be used. It states that the system should be set up using a standard type of phone line commonly found in most business settings. This ensures compatibility and reliability.

Remember, however, the exemption from 26.6.4.2 that we covered a few sections ago. In modern times, there are alternatives to traditional voice phone lines that are acceptable.

Required Verification of Communication Integrity

The integrity of the communication between the DACT and the monitoring station is required in "26.6.4.2.2 Signal Verification."

For a reliable information exchange between your DACT and the receiving end, it is crucial to ensure accuracy and trustworthiness.

According to NFPA 72, this communication should take place through a digital code or another approved method, with checks such as signal repetition or digital checks to prevent any loss of data.

Priority and Protocol of DACT Transmission

The DACT's behavior in an emergency is governed by a set protocol. According to the code:
"26.6.4.2.3.1 A DACT shall be configured so that, when it is required to transmit a signal to the supervising station, it shall seize the telephone line..."

In case of an emergency, the DACT will take control of the phone line. It will disconnect any ongoing calls and prevent new ones in order to promptly transmit its alarm signal. This action may seem disruptive, but it is necessary to ensure the immediate communication of the alert.

People ask "where's the fire?" jokingly when you're in a needless hurry. For a DACT attempting to dial, there truly is a fire emergency.

Redundancy and Reliability

In the high-stakes arena of fire safety, having a fail-safe system is not just an option. You're required to have a highly reliable system.
"26.6.4.2.3.3* A DACT shall have means to reset and retry if the first attempt to complete a signal transmission sequence is unsuccessful."

This section of the NFPA 72 code acknowledges that technology, although dependable, is not infallible. Having a backup plan is vital. This provision ensures that a DACT doesn't simply stop working after one failed attempt to send an alarm signal. It is required to keep trying, thereby enhancing the reliability of the fire alarm system.

What Happens When Your DACT Fails?

But what if a DACT can't do its job even after multiple tries?
"26.6.4.2.3.4 If the maximum number of attempts to complete the sequence is reached..." (details describing the next steps)

It is crucial that such failures are not ignored. The system should indicate to the premises that communication has not been established. This prompts human intervention, ensuring that the problem can be addressed before it potentially becomes a disaster.

Channel Transmission Requirements

DACT isn't just about sending signals — it's about how those signals travel.
"26.6.4.2.4 Transmission Channels" mandates that DACTs have at least one of the prescribed transmission channels, and possibly a backup. This could mean anything from standard phone lines to wireless radio channels. The point is to have robust options, and perhaps more than one depending on your situation. That way, if one channel fails, another can take over. That ensures the signal reaches the monitoring center.

"26.6.4.2.5 DACT Transmission Means" expands on the different ways a DACT can send its critical information. Having multiple avenues for sending an alarm is like having different escape routes in a building. If one is blocked, others are available. This part of the code underlines the necessity for having a "Plan B", "Plan C", and so on.

Testing and Maintenance

Finally, none of the advanced technology in a DACT is useful if it fails to function properly when required. Regular checks are required by NFPA 72, which specifies:

"(6) Each transmission means shall automatically initiate and complete a test signal transmission sequence..."

Routine testing ensures that each transmission method is always prepared for immediate use. Maintenance is not just about compliance, but also a continuous commitment to safety.

Proper DACT Installation and Maintenance is Your Responsibility

Throughout this deep dive into the NFPA 72 code, we've uncovered the intricate details that make DACTs so essential in modern fire alarm systems. They're quietly waiting in the background until they're called upon in an emergency. Complying with NFPA 72 isn't just about checking a box on your checklist. You need to get this right to ensure public safety.

Technology is constantly pushing the boundaries of fire safety. As we embrace these advancements, we must also embrace the guidelines that ensure they work as intended.

DACTs, with their complex protocols and requirements, show how a well-regulated system can bring peace of mind. It's not just about the technology. It's about creating a safe and responsive environment for when disasters occur.

Fire alarm systems with DACTs demonstrate how much we've progressed in protecting what matters most. Adherence to NFPA 72 is the golden thread that ties this progress together.

Call Digitize for Help with Your Fire Alarm Project

At Digitize, we have extensive experience with designing and (through our nationwide distributor network) installing fire alarm systems that comply with NFPA 72 standards.

If you need assistance with your next fire alarm project, don't hesitate to call. Our team of experts will work closely with you to ensure that your next project is a full standards-compliant success.

Call a Digitize engineer now at 1-800-693-0351 or email info@digitize-inc.com

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