Definition

Alarm communicator

Also known as: DACT, digital alarm communicator transmitter, dialer, cellular communicator, dialer capture module

An alarm communicator is the component that carries an alarm panel's signals to the supervising station. The classic form is the DACT — a digital alarm communicator transmitter that dials out over a phone line — while modern communicators send the same events over cellular or IP paths.

How it works

A DACT seizes its telephone line, dials the receiver, and transmits events in a signaling format such as Contact ID or SIA. Cellular and IP communicators either replace the DACT outright or capture its dialer output and re-carry it over the new network. Once signals leave the dial-up rules behind, NFPA 72's performance-based transmission requirements — including supervision intervals for detecting a lost path — apply to the new communicator.

Why it matters

The communicator is exactly the piece copper retirement forces you to rethink. Whether a site keeps its DACT behind a POTS-replacement appliance or swaps in a listed cellular communicator determines which code requirements apply and what the authority having jurisdiction will want to see documented.

Common use cases

Fire alarm panels reporting to a central station over a DACT
Burglar panels re-carried over cellular after a copper line is retired
Dual-path (cellular + IP) communicators for supervised transmission

The practical question for any migration is not “does the panel still dial?” but “does the whole path — panel, communicator, network, receiver — still meet the supervision and signaling rules the account is monitored under?”

Testing the whole path, not the dial-out

A panel that reports “communication OK” has only confirmed it reached something. Verify the full chain during a migration by placing a real test signal and confirming receipt at the supervising station by account number and zone — not by watching the panel’s own display.

Three mismatches account for most post-migration failures. The signal format the panel transmits must be one the receiver decodes; a panel set to an older pulse format may dial successfully and still deliver nothing the receiver understands. The supervision timer configured at the station must match what the new path can sustain. And the account number must be unchanged, or signals arrive and get discarded as unrecognized.

Coordinate the test window with the station in advance, and ask them to confirm in writing which signals arrived and when. That written confirmation is the artifact an inspector will ask for, and it is far easier to obtain on the day of the cutover than three months later.

Common misconceptions

“Keeping the existing DACT means nothing about the installation changes.”

The DACT keeps its dialing behavior, but the transmission path behind it changes — and the path's supervision, listing, and acceptance are evaluated under the code rules for the new technology, not grandfathered under the old dial-up rules.

Frequently asked questions

Is a POTS-replacement appliance an alarm communicator?

Functionally it can serve as the transmission path a DACT dials into. Whether that arrangement is acceptable for a given system depends on the panel, the signaling formats in use, the appliance's certifications, the code edition, and the authority having jurisdiction.