A decorative device is disclosed which includes a motor, music module or other electrical loads and electrical circuitry and a connector for connection to a selected socket of a string of conventional sockets for connection to an A.C. line. The connector includes an elongated flexible cable and is constructed to permit ready installation and positioning. Lamps may be provided in the device. The electrical circuit includes a bridge rectifier and Zener diodes connected to insure continuous energization of lamps of the string while protecting against excessive voltages and minimizing safety hazards.

A string set of series-connected incandescent flasher type lamps in which substantially all of the lamp filaments in the set are individually provided with a voltage regulated shunt circuit, which includes a voltage responsive silicon semiconductor device, which operates in one of two conducting states, neither of which is greater than about 200 ohms. When the flasher lamp is in the "on" or illuminated state, the silicon semiconductor voltage regulating shunt device is in a low impedance state. When the flasher is in the "off" state, the impedance of the silicon semiconductor device is in a lower impedance state equal to or slightly greater than the parallel equivalent impedance of silicon semiconductor device in parallel with the normal operating impedance of the flasher lamp.

A process for fabricating Zener diodes that does not require the use of photomasks. An oxide layer is grown on a silicon substrate which is doped with an N-type dopant. The substrate is subsequently implanted with a P-type dopant, forming a PN junction. The substrate is then metallized for connecting the Zener diode to other circuit components. Advantageously, the substrate may be scribed after processing, before processing, or anytime during processing. Back-to-back Zener diodes formed in this manner are used as shunt circuits across individual lamp sockets in series-wired Christmas light strings to maintain current flow to each of the lamps of the light string when one or multiple lamps fail.

A series-connected string of incandescent light bulbs, operating on half-wave or full-wave rectified DC voltage, each having connected thereacross a filament voltage regulating shunting circuit which regulates the voltage across an empty or otherwise inoperative socket at substantially the same value as that across each of the remaining sockets in the string, thereby insuring continuous illumination of the light string. The voltage regulating shunting circuit of the present invention is a diode array formed of a plurality of series-connected silicon diodes and can be mass produced by using conventional manufacturing techniques at an ultimate selling price of approximately one cent.

A string set of series-connected incandescent bulbs in which substantially all of the bulb filaments in the set are individually provided with a shunt circuit which includes a voltage responsive switch which is inoperative during normal operation of the string set when connected to a source of operating potential and which becomes operative only in response to an increase in the voltage thereacross which exceeds its rating, and in which the remaining bulbs of the circuit continue to receive current therethrough and continue to be illuminated at substantially constant illumination even though other or substantially all of the other bulbs in the string are either inoperative or are missing from their respective sockets.