The Polarity Rectification Tripods (also known as Tripod Traps) are electromagnetic devices combined with camera tripods used to rectify a straight polarity reversal. 
Primary Canon History
In late 1989, some kind of major P.K.E. storm blew through Orrefors and affected the silicon molecules in the glass for sale. As a result, the very expensive glass items floated in mid-air. The Ghostbusters utilized the Polarity Rectification Tripods to neutralize the psychic disturbance. They set up one tripod in each of the four corners of the main display case. On Egon Spengler's word, Winston Zeddemore and Ray Stantz threw the switches. The tripods activated and lasers shot out. They effectively neutralized the glass but they simply came crashing down and shattered into pieces.
Secondary Canon History
In December, Egon Spengler began a more serious investigation of the Red Lightning strikes in New York. To aid in the collection of data, Egon rigged several Polarity Rectification Tripods, some modified, on the roof of the Firehouse. One of the tripods was kept on top of one of the lockers in the garage bay.
- On June 19, 2016, the four props and power supply hub went up for auction with a starting bid of $2000 as 'Force Field Generators.' It was described as "constructed of plexiglass, resin, metal, cable, industrial electronics, and repurposed existing gauges and lights. Consisting of (4) identical transmission towers set on steel tripod bases measuring 42 in. tall x 16.5 in. wide at the tripod feet. Each with a clear acrylic cylinder housing black and yellow barber-striped transparencies over a light source illuminated from within and topped by a flat black base with 3-ball and joint aluminum and copper rods protruding from the top. The circuit box on each is stencil-numbered from 1 to 4. All towers are attached to the 14 x 7 in. central metal power supply hub by cables and locking jacks. The hub features toggle switches with red plastic flip-up guards, lighting elements and faux buttons at top, industrial engraved serial number plates, and functioning and decorative electronics. This unit, when switched on, powers the entire set up. The hub is wired to an industrial factory-style 4.75 x 2.5 cast resin hand grip controller with toggles and switches that, when depressed, activate electronic features, including lights and electronic meters, on the four tripod devices." 
- In Ghostbusters International #8, on page 17, in panel 2, the Polarity Rectification Tripod resembles as it was seen recently up for auction in June 2016.
- Eisenberg, Adam (November 1989). Ghostbusters Revisited, Cinefex magazine #40, page 22. Cinefex, Riverside, California, USA.
- Profiles in History Lot 1604 retrieved 6/21/16