Abstract: A power converter for providing a selectable desired voltage has a converter circuit having an input port for receiving an input of a first voltage and an output port for providing an output of a second voltage. The converter circuit also has a keyway for receiving a key. The key, which is configured to be received by the keyway, contains an electrical component and has a body within which the electrical component is disposed. The output voltage of the converter is determined by the value of the component disposed within the body of the key such that the output voltage can be varied by replacing the key with another key having an electrical component of a different value.

Abstract: Apparatus for providing integrated test circuits for a smoke detector is disclosed. The smoke detector operates such that products of combustion such as smoke and carbon monoxide cause the resistance across a sensor element to be lowered. The lowered resistance of the sensor element, in normal operation, causes a change in an associated voltage level. When the change in the associated voltage level is sufficiently large, the change is detected resulting in the generation of an alarm signal. In the present invention, a switch or button causes a circuit variation that results in a voltage level change similar to that attained when the voltage across the sensor changes as a result of the introduction of the products of combustion. Activation of the switch or button results in a generation of the alarm signal and tests the operational status of the smoke detector. A multiplicity of embodiments of the present invention are illustrated.