The ESL 449 Series self-diagnostic, four-wire, photoelectric smoke detector is another, potentially life saving, accessory available for the Ray Allen F-Series Heat Alert and Deployment Systems. This smoke detector continually monitors its own sensitivity and operational status. The low-profile design allows you to mount easily and conspicuosly inside your vehicle for maximum protection. Easily connects to the auxillary input of the F-Series unit, providing a quick alert to your pager when away from the vehicle.