A device for finding an inoperative bulb in a series string of lights, such as a string of Christmas tree lights having a plug, a pair of electrically conductive leads connected to the plug and having their ends terminating within a casing of the device, a polarity switch having first and second terminals each connected to a lead of the pair of leads connected to the plug, a probe for insertion into and contact with the wire of the socket of the light string, and an indicator circuit for determining whether an electric current is passing through the series string thus indicating the presence or lack of an inoperative bulb. The indicator circuit is located between the polarity switch and the probe and a protective sheath is provided to prevent any part of the probe from being exposed to avoid a user from being shocked, the protective sheath being continuously biased to cover the probe.

Apparatus for determining which bulb or bulbs in a string of miniature incandescent light bulbs is burned out. The apparatus includes a socket adaptor with wire contacts at the base thereof for making conductive contact with both circuit contacts in the base of a selected bulb socket in the light circuit. Light emitting diodes are located within the adaptor body between each wire contact and a junction connected to one contact of a battery. The other contact of the battery is connected to both contacts of a female receptacle body. The male plug of the light circuit is inserted into the female receptacle of the socket adaptor, thus placing both ends of the string of bulbs in connective communication with one contact of the battery. The diodes are located in the socket adaptor body so that when either diode lights up, the direction in the light circuit of the inoperative bulb is indicated.

A piezoelectric circuit (10, 70, 100) is provided which can be employed in a wide variety of applications. The circuit (10) can be used to test the bulbs in a string (14) of Christmas Tree lights and, in a modified circuit (200) can use any suitable high voltage source (202) as a substitute for the piezoelectric crystal. The circuit (100) can also be mounted in a shoe (64), fishing lure (46), toy (56) or any other suitable application to light a light source (19). In another circuit (70) by positioning a capacitor (72) in parallel with the crystal (16) and light source (62), and positioning a normally open switch (74) between the capacitor and light source, the capacitor can be charged by repeated striking of the crystal. The circuit (70) can be used in the pedal (30) of a bicycle to generate a flashing light easily visible at night. The circuit (70) can also be mounted in a camera (90) or emergency light (36) or any other suitable application.

A piezoelectric circuit (10, 70, 100) is provided, which can be employed in a wide variety of applications. The circuit (10) can be used to test the bulbs in a string (14) of Christmas tree lights and, in a modified circuit (200) can use any suitable high voltage source (202) as a substitute for the piezoelectric crystal. In another circuit (100) a capacitor (72) is used to store electrical power to light a light source (19) for a period of time after the piezoelectric crystal is struck. The circuit (100) can be mounted in a shoe (64), fishing lure (46), toy (56), or any other suitable application to light a light source (19). In another circuit (70) by positioning a capacitor (72) in parallel with the rectified output of crystal (16) and light source (62), and positioning a normally open switch (74) between the capacitor and light source, the capacitor can be charged by repeated striking of the crystal. For light sources ( 62) that require a trigger voltage, a normally open switch (75) is mounted between the crystal (16) and the light source trigger contact (120). The circuit (70) can be used in the pedal (30) of a bicycle to generate a flashing light easily visible at night. The circuit (70) can also be mounted in a camera (90) or emergency light (36) or any other suitable application.