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USING THE GENTEX GN-503FF COMBINATION SMOKE AND 

CARBON MONOXIDE ALARM ALLOWS THE ABILITY TO: 

• Interface with a FACP Panel

• Interface with NAC Circuits

GN-503FF ADDITIONAL PRODUCT INFORMATION

Use brown/yellow wire to tandem interconnect GN-503FF alarms to additional GN-503 Series, S1209 Series and CO1209 Series.

NOTICE: THE GN-503FF IS ONLY CAPABLE OF TANDEM INTERCONNECT WITH GN-503 SERIES, CO1209 SERIES AND 
S1209 SERIES. 

THE GN-503F AND GN-503FF PRODUCT WIRING HARNESS IS NOT INTERCHANGEABLE.  THE GN-503F AND GN-503FF
MUST USE PROPER WIRING HARNESS.  PRODUCT WILL NOT FUNCTION  IF INCORRECT HARNESS IS USED.

DO NOT connect Gentex alarms to other manufacturers’ alarms.

Per NFPA 72, a maximum of 18 compatible smoke, heat, CO and/or combination smoke/CO alarms may be interconnected. No 
more than 12 of the 18 can be smoke alarms. 

All units connected in tandem MUST get their power from the same circuit, that is, all smoke alarms in tandem must be 
controlled by the same fuse or circuit breaker.

NOTICE: PER NFPA 72, A MAXIMUM OF 12 SMOKE/CO ALARMS OF GN-503 WITH THE RELAY OPTION (FF) MAY BE 
TANDEM INTERCONNECTED.

C

CA

AU

UT

TIIO

ON

N:: BROWN/YELLOW wire to be capped when not in use. This wire is for tandem connection only. Do not connect to any

other circuit. 

If smoke alarm portion of device goes into alarm, all smoke alarms, CO alarms or combination smoke/CO alarms tandem wired 
will sound smoke alarm warning.

When both smoke and CO conditions are present, smoke condition will have priority and alarm will sound smoke annunciation.

GN-503FF Wiring Diagrams

PLUG

SMOKE/CO
ALARM

BLK

WHT 

VIO

VIO 

ORN

YEL

HOT

NEUT

POWER

SMOKE ALARM
CONTACTS (FORM A CONTACT)

BRN / YEL

TANDEM

SMOKE FORM C COMMON

SMOKE NORMALLY CLOSED

CO ALARM
CONTACTS (FORM A CONTACT)

PINK

PINK

BLU

GRAY

VIO / YEL

FORM C
ALARM
CONTACTS

SMOKE & CO NORMALLY OPEN

CO FORM C COMMON

CO NORMALLY CLOSED

ELECTRICAL

 

BOX

SMOKE/CO

ALARM

QUICK DISCONNECT

TYPE PLUG

HOT / BLACK

NEUTRAL / WHITE

TANDEM WIRE

BRN / YEL

SMOKE/CO

ALARM

ELECTRICAL

 

BOX

ELECTRICAL

 

BOX

SMOKE/CO

ALARM

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