A smoke detector of the type utilizing photo-electric detection of light reflected from smoke particles, in which a light-generating device is energized intermittently and a photo-responsive device and an associated amplifier produce energy pulses when smoke is present. The energy pulses are utilized to actuate an alarm. To prevent power supply voltage changes from affecting the operation of the amplifier, a capacitor is provided across the power leads to the amplifier, and means is provided between the capacitor and the power supply for electrically isolating the amplifier and capacitor from the transient voltages from the power supply, which are caused by the turning on of the light generating device, or from other causes. In one embodiment of the invention said means comprises a choke coil in the line to the capacitor and a second choke coil in the line to the light generating device. In another embodiment of the invention the isolating means may be Zener diodes in place of choke coils. In a third embodiment of the invention the means comprises a switch in the power line between the capacitor and the power supply, with means being provided to open the switch when the light generating device is energized. In each embodiment, the amplifier is isolated from transient voltage changes during the time the light generating device is energized, so that the pulse of energy required to power the amplifier is provided by the capacitor.

The present invention discloses improved smoke detector devices. In a preferred embodiment, the invention takes the form of an improved smoke detector of the type having a ceiling-mounted, main housing with an electrical circuit that includes an alarm device and a smoke sensing means that activates the alarm device when smoke is present in the vicinity of the sensing means. Wherein the improvement comprises a remote housing that is remotely disposed from the main housing, with the remote housing having affixed thereto a remote electrical circuit comprising a means for receiving an electrical connection from the main electrical circuit, a means for testing the operating condition of the main electrical circuit, a means for shutting off the alarm device, and a remote battery coupling means that allows a battery for powering the detector to be located in the remote housing. In another embodiment, the invention takes the form of a smoke detector remote unit, for use with a retrofitted, improved smoke detector, for providing the detector with remote testing, shutoff and powering capabilities.