Abstract: A protector for well tools such as drill pipe tubing, and the like, which is positionable about a joint of a drill pipe or tubing and which is moved into pre-determined position on the box-half of a tool joint by the pin-half of the tool joint as it is moved into telescoped and threaded engagement with the box-half.

Abstract: A power controller for transmitting alternating current from a power input circuit to a load, the controller being a master silicon controlled rectifier, hereinafter the "master rectifier," and a slave silicon controlled rectifier, hereinafter the "slave rectifier," connectible in parallel with the load across the input circuit, a capacitor chargeable during positive half cycles for discharging at the zero voltage crossover between half cycles of positive and negative input voltage to render the master capacitor conductive and a second capacitor chargeable When the master controlled rectifier is conductive whose discharge renders the slave rectifier conductive at the instant of zero voltage crossover between half cycles of negative and positive input voltage.