Model SIH-24F

Ionization Type Smoke Detector The SIH-24F has responsive, yet high operational stability for an extremely wide range of uses. The SIH-24F can be used in areas where early warning of trouble from super-heated or flaming combustibles is expected. The SIH-24F is also constructed to be effectively used where RF and other electrical interference is expected to be encountered.

HSB-224, HSB-224R or HSC-4R bases may be used with the SIH-24F. Current interchangeable devices are SLK-24F and SLK-24FH.

The SIH-24F ionization smoke detector has two chambers: a sampling chamber and a reference chamber. Smoke or invisible combustion gases can freely penetrate the sampling chamber, but the reference chamber is virtually closed to prevent easy entry. With both chambers ionized by a single radioactive source, a very small current flows. Visible smoke or invisible gases present greatly influence the current flow in the sampling chamber, changing the voltage ratio between the chambers. This difference is amplified inside the detector. After reaching the critical level, the detector triggers into alarm.

The SIH-24F includes a status LED which blinks approximately once each second, indicating the head is powered. The status LED lights continuously during the alarm period.


  • Low profile, 1.9 inches including base
  • 2- or 4-wire base compatibility
  • Highly stable operation
  • RF/transient protected
  • Low standby current, 4OuA nominal
  • Built-in power/alarm LED Non-directional smoke chamber
  • Vandal resistant security locking feature
  • Built-in magnetic detector sensitivity test feature
  • Interchangeable with SLK-24F and SLK-24FH Photoelectric Detectors
  • Relay bases available


  • Radioactive Source: AM-241 0.5uCi
  • Rated Voltage (4-wire): 15.0-30.0 VDC
  • Working Voltage (2-wire): 15.0-33.0 VDC
  • Supervisory Current: 4OuA at 24 VDC
  • Surge Current: 2OOuA at 24 VDC
  • Alarm Current: l5OmA at 24 VDC (Base specific)
  • Ambient Temp: 32F - 120F (0C - 49C)
  • Mounting: 4" SQR, 4" OCT, 3" OCT with adapter ring


HSB-224 SMOKE DETECTOR BASE The HSB-224 Smoke Detector Base is designed for use with Silent Knight Smoke Detector Model SIH-24F The HSB-224 is a 6-inch polarized base with annunciator output featuring a current limiting resistor, transient protection, and a blocking diode to enhance annunciator function. The HSB-224 is available for applications not requiring current limiting.


HSB-224R AND HSC-4R SMOKE DETECTOR BASES The HSB-224R and HSC-4R Smoke Detector Bases are designed specifically for use with Silent Knight Smoke Detector Models SIH-24F, SLK-24F, SLK-24FH. Both are 6-inch bases with two Form C (DPDT) contacts (1 amp at 3OVDC and 0.5 amp at 125VAC) where relay contacts are required as a function. Underwriters Laboratories approved for releasing device service.