Abstract: A string of lights has an electrical plug at one end and a receptacle at the other end and plural light-emitting diodes (LEDs) in series with a negative temperature coefficient (NTC) thermistor. The device also includes a bridge rectifier providing direct current to the LEDs and the thermistor but split between the plug and receptacle of the light string so that alternating current from the plug is delivered to the receptacle but direct current flow through the LEDs. Light string fuses protect the string but the NTC fuses protect the LEDs at a lower current rating. The LEDs can be arranged in a simple electrical series, or, in an alternative embodiment, an electrical series of groups of plural LEDs each of which is arranged electrically in parallel with other LEDs of the same group.

Abstract: A light for use in light strings has a deeper socket, a longer base and longer Dumet wires than a standard socket, base, and Dumet wires so that the standard bases and bulbs will not operate in the non-standard socket. Furthermore, the base and sockets are keyed so that they are restricted to at most two orientations with respect to each other and cannot be twisted with respect to each other.

Abstract: A single circuit element, referred to as a solid state rectifying fuse (SSRF), rectifies an incoming AC signal and opens the circuit if a programmed maximum current level is reached. The anode or cathode depending upon the particular application is designed with a plurality of conductors strips in electrical contact with the P or N region, respectively. Conductor strips are composed of a material that melts open if the current limit is exceeded. Conductor strips are designed to have a lower total current handling capacity than that of the PN junction so that the current is reduced or terminated before the PN junction can “short.” Depending on the desired maximum current of the SSRF, the current limit can be adjusted downward by burning out or severing some of the conductors. In this sense, it is a programmable diode.

Abstract: A light socket is disclosed that has a built-in integrated circuit for rectifying the alternating current received from an electrical outlet and limiting the direct current produced. The light socket is specifically suited for low-current, low-voltage applications such as supplying DC to a string of ornamental lights. The integrated circuit has a diode with a modified cathode that acts as a fuse as it is rectifying the alternating current. The cathode is formed of a plurality of electrically parallel conductors. Excessive current blows out at least some of these conductors in the same way a conventional fuse blows. Various embodiments add other current-limiting elements, elements for producing full wave or near will wave rectification, and for opening the circuit when they detect extraneous currents.