How Wireless Interconnected Smoke Alarms Work (and Why They Matter at Night)

Quick answer

Wireless interconnected smoke alarms talk to each other over radio. When any alarm in the group detects smoke, it broadcasts a signal and all alarms sound at once, so you hear the warning wherever you are in the house. The Heiman S1-R uses a proprietary Sub-1G FSK protocol at 915 MHz, with a rated range of up to 800 ft in open areas.

The problem interconnect solves

A single alarm only protects the space it can "smell." A fire in a basement, garage-adjacent room or far wing may produce an alarm that bedroom occupants cannot hear through closed doors. Interconnect turns separate devices into a whole-home system: the first alarm to sense smoke alerts everyone.

Wired vs. wireless interconnect

Traditional interconnect uses a dedicated wire between units, which usually means cutting into walls and ceilings. Wireless interconnect replaces that wire with a radio link. For many homes, especially existing ones, this removes the main barrier to adding interconnected protection.

How the S1-R builds a network

There are two ways to link alarms:

1. With a gateway. Add the S1-R as a sub-device to a compatible Heiman Smart Gateway (for example, WS3GW-R) in the Heiman Home app. Once added, all connected alarms form an interconnected network, and the app delivers real-time notifications.

2. Without a gateway. One alarm becomes the "host" and others join it by button presses on the Reset button, confirmed by LED and beep patterns. The manual notes that other compatible devices (such as CO alarms, heat alarms and remote controllers supporting the same wireless feature) can join the same group.

See our setup tutorial for the exact button sequences.

The host device doubles as a repeater

In a direct-link group, the host device also acts as a repeater. To extend coverage, place the host in a central location of the house. The 800 ft rating applies to open areas; walls, floors and appliances will reduce real-world range, so test after installation.

How many alarms can you link?

The manual states up to 24 safety devices may be interconnected in a multi-station arrangement, but the system must also comply with NFPA 72 limits:

· No more than 12 smoke alarms.

· No more than 18 alarms in total (smoke, CO, combination, heat, etc.).

· When 18 alarms are interconnected, you may add up to 6 remote signaling devices and/or relay modules.

Testing the interconnect

Activate the test on any one alarm (press and hold the test button for more than 1 second). If the link works, every other paired alarm sounds at the same time. If one stays silent:

1. Confirm it is powered and within wireless range of another paired alarm.

2. Check that it appears online in the Heiman Home app.

3. Re-pair it by repeating the pairing procedure.

The manual's troubleshooting guidance also suggests moving a non-responsive alarm closer to other units to improve reception.

Test each unit individually

For wirelessly interconnected systems the manufacturer recommends testing each unit during the weekly test to verify both its own function and the interconnection signal.

Important safety note on remote silencing

If a remote silencing function is available, it may only be used when there is no genuine fire emergency and the smoke alarm is within your line of sight.

FAQ

Do I need Wi-Fi? Direct alarm-to-alarm linking does not need a gateway or app. The gateway and app add notifications.

Can I mix alarm types? The manual says the S1-R can group with compatible devices that support the same wireless feature, such as CO alarms and heat alarms.

What if I move an alarm? Remove it from the network (press Reset 10 times) and re-add it, then retest.

A night-time example

Imagine a three-level home. A fire starts in the basement while the family sleeps on the top floor. A single alarm in the basement would sound, but the sound must travel through floors and closed doors. With interconnect, the alarm in each bedroom sounds at the same moment, so residents have the earliest possible warning. This is the core safety argument for interconnect, and it is why the manual presents the network as a "powerful safety network."

Gateway vs. direct link: which should you choose?

Many households use both: they link alarms directly for reliability and add a gateway for notifications when away.

Practical range tips

· The 800 ft figure is for open areas. Indoors, building materials reduce range.

· Put the host device centrally and test each unit.

· If a device does not respond, move it closer to another interconnected unit to improve signal reception, as the manual's troubleshooting table suggests.

Mixed alarm groups

The manual says this alarm can group with compatible devices such as CO alarms, heat alarms, and remote controllers that support the same wireless feature. Because group limits apply (12 smoke alarms, 18 total alarms), plan your layout before you buy.

Common misconceptions

"Wireless means it relies on Wi-Fi." The S1-R uses a proprietary low-power radio protocol at 915 MHz, not your home Wi-Fi, for alarm-to-alarm communication.

"If one alarm is faulty, all fail." Each alarm still senses smoke on its own. But a unit that is not paired or is out of range will not sound with the group, which is why you test each unit.

About this guide 
Written by [wing,product engineer]. Technically reviewed by [Reviewer name, product manager]. Based on the Heiman S1-R Smoke Alarm User Manual (M416-40E, Ver 1.2) and the NFPA 72 guidance it cites. Last updated: [YYYY-MM-DD]. This article is general information, not a substitute for the manual that ships with your device or for your local building and fire codes.