Abstract: A string of miniature holiday lamps connected in a series circuit with each lamp having an indicating device connected in parallel to its respective lamp. The indicating device is operated in response to the non functioning of the lamp with which it is connected in parallel. When the lamp fails, the full line voltage of the series circuit passes through the indicating device causing it to activate, signaling the non functioning lamp. The signaling device can be a resistor associated with a thermochromic paint that changes color when activated by the heat from the resistor, a sound alarm, an odor activated device or an electroluminescent light. In another embodiment the signaling device can be used to indicate a circuit having a resistive load is energized.