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Gentex GN-503FF, 120V AC PE Smoke/CO Detector, 2 Form A/C Relays, 9VDC Backup
Gentex GN-503FF, 120V AC PE Smoke/CO Detector, 2 Form A/C Relays, 9VDC Backup

Gentex GN-503FF, 120V AC PE Smoke/CO Detector, 2 Form A/C Relays, 9VDC Backup

Manufacturer Part#:918-0021-002
Our Part#:918-0021-002
Stock Status: Call for Availability
Retail Price:$116.03
Your Savings:$25.73(22%)
Your Price:$90.30









Feature 5


Feature 7

Product Type:Combination Detector|Input Voltage:120VAC|Detection Type:Photoelectric + CO|Connection Type:Hardwired|Intended Use:Residential,Commercial|Battery Backup:Yes|Interconnect:Yes


  • Features Two (2) Sets of Form A/C Contacts that Activate Independently for Smoke and CO Events
  • Relay contacts operate on battery back-up
  • Differentiating Signal for Each Alarm Type Annunciation
  • Photoelectric Smoke Sensor and Electromechanical CO Sensor
  • 120VAC with 9VDC Battery Back-Up
  • Push Button Self-Test Feature
  • Quick-Disconnect Wiring Harness
  • Non-latching (self-restoring) Alarm
  • Tandem interconnect with Gentex GN-503, GN-503F, CO1209, CO1209F, S1209 and S1209F
  • Temporal 3 Evacuation Sound Pattern for Smoke Annunciation
  • Temporal 4 Evacuation Sound Pattern for CO Annunciation
  • End of Life Signal Indicates CO Sensor has Reached Depletion State
  • Listed to ANSI/UL 217 and ANSI/UL 2034
  • NFPA 72 and NFPA 720 Compliant


The GN-503 (120VAC/9VDC) Series of combination photoelectric smoke and electrochemical sensor carbon monoxide alarms are for use as an evacuation device 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 UL 217, UL 2034, for installation per NFPA 720 and NFPA 72.

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 Gentex GN-503 Series are provided with a self test and functionality test feature. The self test notifies if the smoke/CO alarm is functioning properly or needs attention. The functionality tests that the smoke/CO alarm is operating properly. The self and functionality tests are in compliance with NFPA 72 and UL Standards.

Features of the combination alarm series include DUALINK® differentiating tones indicating a smoke alarm (temporal 3) or a CO alarm (temporal 4), tandem capabilities with all Gentex tandem interconnect capable alarms. Options include a Form A/Form C dry contacts for remote annunciation and connection to a protected premises alarm system to provide a supervisory/trouble signal. The GN- 503 provides Temporal 3 evacuation tone for smoke alarm and all units provide Temporal 4 tone for CO alarm annunciation. The Temporal 3 evacuation tone for smoke alarm will take precedence of the Temporal 4 tone for CO alarm.

Electrical Specifications

Operating Voltage 120VAC, 60Hz
Operating Current .045 amps
Operating Current (Relay Options) .070 amps
Operating Ambient Temp Range 40°F to 100°F
Alarm Horn Rating 85dBa at 10 feet
Auxiliary Relay 1 Form A & 1 Form C (0.6 amp)
Size Diameter: 6.25 in OA (5.75 in. at ceiling)
Secondary Power Source Alkaline 9VDC battery Duracell MN 1604
CO Sensing Cell Electromechanical Cell

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