Honeywell HFS-P Category : HoneywellOddly enough, the model number on this particular smoke doesn’t fit the typical pattern for Honeywell devices.
GE 521BXT Category : GEI think that this smoke detector might be intended for use in security systems.
Simplex 477-669 Category : SimplexOddly enough, the model number on this particular smoke doesn’t fit the typical pattern for Simplex devices.