Abstract: A portable monitoring system for detecting a radiated electrostatic field and producing an audible warning when the detected field exceeds a selected value is characterized by a switching device which can be used to reset the threshold warning level and which is not affected by the hand proximity effect. An alarm is sounded when a signal corresponding to the detected field exceeds a value which is stored. The stored value can be reset by a manually operated switching circuit including a delay device operable to delay the storage of a reference level corresponding to the intensity of the field currently detected.

Abstract: An electric field strength indicator for use with high voltage conductors comprises a capacitive probe mounted within a tubular shield having an insulating spacer at one end for locating the unit with respect to a conductor under test. The probe is electrically coupled to a signalling circuit and is movable axially within the shield to a position at which a threshold response is obtained. Such position, which denotes the conductor voltage, is read on a scale provided. Because of the shield the device is directional, the probe being shielded from neighboring conductors.