Gentex GN-503


Combination Smoke/CO Alarm, 120VAC, 9VDC Battery Back-Up

Availability: In Stock

  • Factory New
Brand: Gentex Part #: Q01B-0891 Categories: , Manufacturer Part #: GN-503


The GN-503 (120VAC/9VDC) Series of combination photoelectric smoke and electrochemical sensor carbon monoxide alarms are for use as evacuation devices in all dwelling units, including but not limited to homes, apartments, hospitals, hotels, motels and other commercial occupancies. The GN-503 Series is listed in compliance with ANSI/UL 217, ANSI/UL 2034, for installation per NFPA 720 and NFPA 72.

Available in three models, the GN-503 Series is engineered to virtually eliminate nuisance alarms and deliver outstanding performance wherever reliable smoke and CO protection is required. The GN-503F features one (1) set of Form A/Form C contacts that activate for smoke and/or CO events. The GN-503FF features two (2) sets of Form A/Form C contacts that activate independently for smoke and CO events. Both the GN-503F and GN-503FF provide a connection to a protected premises alarm system to provide a supervisory/ trouble signal.

The GN-503 Series is provided with a 9VDC alkaline battery for electrical back-up in the event building power is lost. The battery impedance is verified and the alarm provides a low or missing battery warning. The battery drawer provides easy replacement without removing the unit from the wall or ceiling.

The GN-503 Series is designed with a self test feature that quickly notifies if the alarm is functioning properly or needs attention (signified by a series of chirps) by simply pressing the test button. The functionality tests that the smoke/CO alarm is operating properly (signified by going into alarm). The self and functionality tests are in compliance with NFPA 72, NFPA 720 and ANSI/UL Standards.

The GN-503 Series provides a temporal 3 evacuation tone for smoke alarm annunciation and all units provide a temporal 4 tone for CO alarm annunciation. Per NFPA 720, the temporal 3 evacuation tone for smoke alarm will take precedence over the temporal 4 tone for CO alarm.


Weight 0.2 lbs
Dimensions 1.80 × 6.25 × 6.25 in





Production Status



  • GN-503 available in 120VAC with 9VDC battery back-up
  • Horn frequency 3100 Hz (nominal)
  • Meets sensitivity requirements of ANSI/UL 2034
  • F Model: One (1) set of Form A/Form C contacts that activate for smoke and/or CO events
  • FF Model: Two (2) sets Form A/Form C contacts that activate independently for smoke and CO events.
  • Relay contacts operate on battery back-up
  • Push button self test feature
  • Push button functional test feature
  • Quick-disconnect wiring harness
  • Non-latching (self restoring) alarm
  • Fully insect protected
  • Red LED pulses every 30 seconds, green LED for AC power on
  • Mounting hardware adapts to standard junction boxes, including but not limited to 4x4x2-1/8 octagon
  • Dust cover to prevent contamination during installation
  • Low or missing battery indicator
  • 1 year warranty from date of purchase
  • 5 year limited warranty on CO sensor

GN-503 Series; 120VAC/9VDC Single/Multiple Station Carbon Monoxide Alarm

Gentex - Data Sheet

GN-503 Series; Combination Photoelectric Smoke & Carbon Monoxide (CO) Alarm

Gentex - Installation Instructions