Abstract: A principal object of the invention is to detect sparks or arcs (12) in electric circuits (13) or otherwise to detect a signal having a spectrum of a broad band of distinct instantaneous radio frequencies in radio frequency noise. The invention rejects extraneous narrow-band signals having frequencies within the broad band, such as by means of filters (21, 27, 29) or a balanced mixer arrangement (32-39). The mixer 37 may be fed from a radio frequency signal unbalanced to balanced converter (32) having an input (25) coupled to a source of the signal having the spectrum and having balanced outputs connected to the mixer inputs (35, 36). Alternatively, the radio frequency mixer (37) may receive the output of a wide band noise generator (68) at its other input (36, FIG. 5).

Abstract: A supporting structure of one piece of sheet material constituting a top and several legs depending from that top in one piece has for each of these several legs an angled profile of that one piece of sheet material and in one piece with the top across the entire profile. Such supporting structure may be made of a blank of sheet material forming a pattern having a central portion for the top, first and second portions projecting from a first side of that central portion for first and second legs, third and fourth portions projecting from an opposite second side of the central portion for third and fourth legs, and first and second side panel portions projecting from opposed third and fourth sides of the central portion. These first, second, third and fourth portions are provided, respectively, with lateral ledges of which each is spaced from an adjacent one of the first and second side panel portions by a notch for a butt joint of each of the lateral ledges with an adjacent side panel portion.

Abstract: An electronic equipment rack including a horizontal frame member and a vertical frame member is braced against earthquake damage by means of a metal gusset having a first leg fitting against the horizontal frame member to extend along part of that horizontal frame member, a second leg fitting against the vertical frame member for a first part of that second leg to extend along part of that vertical frame member, a third leg spaced from and extending in parallel to a second part of the second leg, and a fourth leg extending between the second and third legs to abut against another part of the vertical frame member. Solid metal is carried from the vertical frame member to the horizontal frame member by intimately connecting the gusset to the vertical and horizontal frame members.

Abstract: Monitoring an electric power distribution circuit having a rated load capacity includes continually sensing an intensity of electric power supplied through that circuit. In response to that sensing a first signal indicating when electric power is supplied through that circuit at a predetermined maximum current usage below rated load capacity is provided. A second signal indicating a safe loading condition is provided when the sensed intensity is substantially below that maximum current usage. A third signal is provided when the mentioned intensity is at a value between the safe loading condition and the maximum current usage.

Abstract: Electronic circuit breakers safeguard a load connected to a power supply against damage from overload conditions. These circuit breakers interrupt flow of overload currents to the load by instantaneously reducing flow of such current from the power supply to the load to a harmless residual current when that electric current flow exceeds a predetermined value. These breakers also avoid downtime after cessation of such a condition by electronically monitoring that residual current to determine when it is safe to restore electric operating current flow to the load. Flow of electric operating current from the power supply to the electronic equipment is restored in response to the latter determination. Preferably, the monitored residual current is used for automatically switching the electronic circuit breaker and the flow of electric operating current electronically back on, when the electronic monitoring has determined that the overload condition has ceased to exist.