• Plug-in detector line – mounting base included
  • Large wire entry port
  • In-line terminals with SEMS screws
  • Mounts to octagonal and single-gang backboxes, 4-square backboxes, or direct to ceiling
  • Stop-Drop ‘N LockTM attachment to base
  • Removable detector cover and chamber for easy cleaning
  • Built-in remote maintenance signaling
  • Drift compensation and smoothing algorithms
  • Simplified sensitivity measurement
  • Wide angle, dual color LED indication
  • Loop testing via EZ Walk feature
  • Built-in test switch
  • System Sensor’s i3TM series smoke detectors represent a significant advancement in conventional detection.  The i3 family is founded on three principles  Installation ease, Intelligence, and Instant inspection.

Installation Ease.

  • The i3 line redefines installation ease with its plug-in design.  This allows an installer to pre-write the bases included with the heads.  The large wire entry port and in-line terminals provide ample room for neatly routing the wiring inside the base.  The base accommodates a variety of back box mounting methods as well as direct mounting with drywall anchors.  To complete the installation, i3 heads plug-in to the base with a simple Stop-Drop ‘N Lock action.


  • i3 detectors offer a number of intelligent features to simplify testing and maintenance.  Drift compensation and smoothing algorithms are standard with the i3 line, to minimize nuisance alarms.  When connected to the 2W-MOD2 loop test / maintenance module, or a panel equipped with the i3 protocol, 2-wire i3 detectors are capable of generating a remote maintenance signal when they are in need of cleaning.  The signal is indicated via an LED located at the module and the panel.  To read the sensitivity of i3 detectors, the SENS-RDR is a wireless device that displays the sensitivity in terms of percent per foot obscuration.

Instant inspection.

  • The i3 series provides wide angle red and green LED indicators for instant inspection of the detector condition, indicating:  normal standby, out-of-sensitivity, alarm, or freeze trouble conditions.  When connected to the 2W-MOD2 loop test / maintenance module or a panel with the i3 protocol, the EZ Walk loop test feature is available on 2-wire i3 detectors.  This feature verifies the initiating loop wiring by providing LED status indication at each detector.
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Models Available

Two-Wire Models
2W-B2-wire standard
2WT-B2-wire standard with thermal


Four-Wire Models
4W-B4-wire standard
4WT-B4-wire standard with thermal


2W-MOD22-wire loop test / maintenance module
SENS-RDRSensitivity reader
RTRemoval / replacement tool
A77-AB2Retrofit adapter bracket


Smoke detector shall be a System Sensor i3 Series model number_______, listed to Underwriters Laboratories UL 268 for Fire Protection Signaling Systems. The detector shall be a photoelectric type (Model 2W-B, 4W-B) or a combination photoelectric/thermal (Model 2WT-B, 4WT-B) with thermal sensor rated at 135°F (57.2°C). The detector shall include a mounting base for mounting to 3 1⁄2-inch and 4-inch octagonal, single-gang, and 4-inch square back boxes with a plaster ring, or direct mount to the ceiling using drywall anchors. Wiring connections shall be made by means of SEMS screws. The detector shall allow pre-wiring of the base and the head shall be a plug-in type. The detector shall have a nominal sensitivity of 2.5 percent-per-foot nominal as measured in the UL smoke box. The detector shall be capable of automatically adjusting its sensitivity by means of drift compensation and smoothing algorithms. The detector shall provide dual- color LED indication that blinks to indicate power up, normal standby, out of sensitivity, alarm, and freeze trouble (Model 2WT-B, 4WT-B) conditions. When used in conjunction with the 2W-MOD2 module, 2-wire models shall include a maintenance signal to indicate the need for maintenance at the alarm control panel and shall provide a loop testing capability to verify the circuit without testing each detector individually.

Electrical Specifications
Operating VoltageNominal: 12/24V non-polarized
Maximum Ripple Voltage30% peak to peak of applied voltage
Standby Current2-wire: 50 μA maximum average
4-wire: 50 μA maximum average
Maximum Alarm Current2-wire: 130 mA limited by control panel
4-wire: 20 mA @12 V, 23 mA @ 24 V
Alarm Contact Ratings2-wire: n/a
4-wire: 0.5 A @ 30 V AC/DC


LED ModeGreen LEDRed LEDConditionDuration

LED ModesPower-Up Sequence for LED Indication
Power UpBlink every 10 secondsBlink every 10 secondsInitial LED Status indication80 seconds
Normal (standby)Blink every 5 secondsoff
Out of sensitivityoffBlink every 5 seconds
Freeze troubleoffBlink every 5 seconds


Physical Specifications
Dimensions (including base)5.3 inches (127 mm) diameter
2.0 inches (51 mm) height
Weight6.3 oz (178 g)
Operating Temperature Range2W-B and 4W-B: 32°F to 120°F (0°C to 49°C)
2WT-B and 4WT-B: 32°F to 100°F (0°C to 37.8°C)
Operating Humidity Range0 to 95% RH non-condensing
Thermal Sensor135°F (57.2°C) fixed
Freeze Trouble2WT-B and 4WT-B only: 41°F (5°C)
Sensitivity2.5%/ft nominal
Input Terminals14to22AWG
Mounting3 1⁄2-inch octagonal back box
4-inch octagonal back box
Single-gang back box
4-inch square back box with a plaster ring
Direct mount to ceiling



ModelThermalWiringAlarm Current
2W-BNo2-wire130 mA max. limited by control panel
2WT-BYes2-wire130 mA max. limited by control panel
2W-MOD22-wire loop test / maintenance moduleRT: Removal / Replacement tool
SENS-RDRSensitivity readerA77-AB2: Retrofit adapter bracket, 6.6 inch (16.76 cm) diameter