Abstract: An earth drill for use with a vehicle of a type which performs utility pole hole drilling operations is disclosed. The drill attaches to an end of a movable boom mounted on the vehicle. An elongated guide is rotatably attachable to the boom via a rotatable coupling, enabling the drill to be rotated to a convenient angle and fixed using an eccentric shear pin. A drill head is movably mounted for advance and retraction along the elongated guide. A drilling tool is attachable to the drill head and is oriented to drill a hole as the drill head is moved with respect to a ground surface. A stabilizer attached to a lower end of the elongated guide includes anchoring holes for receiving pins which are driven into the ground in order to resist transverse and rotative movement of the guide. The guide can float upwardly during a drilling operation, guided by the pins, and need not be fixed to the ground.

Abstract: A rotary percussion bit comprising a shaft, a plate-like member secured to one end of the shaft, a plurality of relatively distributed, raised sections on one surface of the plate-like member, the raised sections containing a plurality of raised cutting elements, a plurality of projecting ribs around the rim of the plate-like member, and a plurality of exhaust holes through the plate-like member. The raised sections comprise rings projecting from the surface of the plate-like member and filler material disposed within the rings, the cutting elements being disposed in the filler material.

Abstract: A circuit for use with key telephone systems for detecting the presence of either of two different distinctive ringing signals received over a telephone line. After detection a separate distinct visual signal is provided to indicate which of the two signals was received.