Abstract: A device for determining whether electrical equipment carries an alternating current that could endanger maintenance personnel or others in contact with the equipment comprises a conductive probe, a rectifier, a threshold detector and an alarm. The conductive probe makes electrical contact with the equipment, and the rectifier rectifies a fraction of any alternating current carried by the probe as a result of such contact to produce a unipolar signal. The threshold detector responds to the unipolar signal and generates an output signal when the voltage of the unipolar signal exceeds a predetermined threshold. The alarm gives a warning response to said output signal.

Abstract: A tackle block for a cord having a rotatable pulley mounted on a shaft between a pair of legs, there being first and second pulleys mounted on a part of the shaft which is exterior of said legs. A guide sheath formed of a pair of arms is associated with the first pulley and the space between each of the arms and the groove of the first pulley is a minimum necessary for a cord of a certain diameter. The second fixed pulley has its inner plate slidably mounted on the shaft and resiliently biased toward said inner plate, with the inner plate being formed of a material which presents a large amount of friction to the cord. A guide means in the form of a pair of arms, each having a notch is provided on the outer face of the movable plate of the second fixed pulley to lock the cord. A braking shoe is mounted in a movable manner below the rotatable pulley to engage the rotatable pulley.

Abstract: A hoisting device, in particular a block, comprises a case having a shorter side and a longer side. A rotatable sheave is rotatably mounted in the case on a shaft that extends between the two sides and projects beyond the shorter side. Two fixed sheaves are mounted on the projecting portion of the shaft. A brake shoe slidably mounted on the longer side of the case below the rotatable sheave is slidable between an upper portion in engagement with the sheave and a lower position disengaged from the sheave. In hoisting condition, a rope passes over the rotatable sheave. In lowering condition, the rope passes from the rotatable sheave, down under the brake shoe and then over the inner non-rotating sheave, thereby pulling the brake block up against the rotatable sheave. In locked position, the rope further passes from the inner non-rotatable sheave around the outer non-rotatable sheave.

Abstract: A pulley having a fixed lateral pulley externally of the blocks thereof for variably braking a line on a rotatable sheave of the pulley.