Interlogix 721U

Photoelectric Smoke detector head only, Two-wire, Output for remote LED

Condition: New
Brand: Interlogix
Status: Obsolete
SKU: 99321
Manufacturer Part #: 721U
Replacement: EC2-OS


The ESL/Interlogix 700 Series conventional photoelectric smoke detector is an interchangeable head and base detector with a light-scattering optical sensor that provides outstanding stability and excellent response to a wide range of fires. A pulsed infrared LED light source and a high-speed photodiode sensing element are housed in an omnidirectional sensing chamber protected by an insect screen.

Additional information

Weight 2 lbs

Production Status



  • Two-Wire and Four-Wire Conventional Photoelectric Smoke and Heat Detectors
  • Advanced alarm verification feature reduces chance of nuisance alarms
  • Automatic drift compensation
  • Head and terminal base design (base sold separately)
  • Low-profile design blends into the ceiling
  • Self-diagnostic capability continually monitors operation
  • Meets NFPA 72 sensitivity test requirements
  • Field-replaceable optical chamber
  • Extensive two-wire compatibility listings
  • Remote LED indicator available for 721U, 721UT and 741UT detectors
  • Compatible with most Kidde, Fenwal and Chemetron Conventional Control Panels (See compatibility chart in Datasheet No. K-70-100)
  • FM Approved
  • UL Listed
  • CSFM Approved


Two- and Four-Wire Conventional Smoke Detectors
Kidde – Data Sheet


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