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Rutt/Etra Scan Processor

Bill Etra showing the Rutt/Etra, circa 1970 (excerpt) (video)
Bill Etra showing the Rutt/Etra, circa 1970 (excerpt) (video)
Tool Identification

Name of tool: Rutt/Etra Scan Processor
Inventor/Designer: Steve Rutt; Bill Etra; Louise Etra
Date of design: 1973
Date of patent: 197?
Country of patent: United States
Date commercialized: 1975
Name of manufacturer: Rutt Electrophysics (New York, N.Y., U.S.)

Historical notice

When he met Steve Rutt in the early seventies, Bill Etra was completing a residency at the WNET Thirteen Laboratory (New York, U.S.) and planning to design a raster scanning processor (an electronic tool manipulating the scanning of the raster in the cathode ray tube) to produce effects of compression and expansion of the video frame. Rutt teamed up with Etra because he hoped to exploit the commercial possibilities of such a device by targeting the audiovisual market. Etra, for his part, was eyeing a clientele of artists and educational institutions. Though neither was a scientist, both had extensive knowledge of electronics. Since the sixties, Etra had used oscillators hooked up to monitors as part of his performances. Rutt had designed stroboscopic devices and was familiar with the components and operating mode of analog computers. Thanks to a grant from the New York State Council on the Arts given to the WNET Thirteen Laboratory (New York) as well as considerable personal investments, Etra and Rutt built a prototype between 1972 and 1973. Louise Etra was involved in every stage of the design and construction.

In the early seventies, scan processors already existed, including Lee Harrison’s Scani-Mate and Nam June Paik and Shuya Abe’s Paik/Abe Scan Modulator. The second device was built from off-the-shelf components, but its AC electric power supply created effects that were hard to control and reproduce. The prototype of the Rutt/Etra Scan Processor based some of its functions on the Paik/Abe but used a DC supply, which did not cause distortions during inputting. In the prototype, Rutt and Etra used an off-the-shelf television monitor connected to the modules via cables. For the final version of 1973, they built the entire screen, which was then integrated with the other modules. In the early seventies, signal processing devices of this type were mainly designed for artists. The Rutt/Etra Scan Processor was an exception because its designers marketed it under the company name Rutt Eletrophysics in 1973 and even considered mass-producing it. Yet this marketing venture failed given that the cost of producing copies was too high and the demand for such a device inexistent in television broadcasting. Videomakers like Gary Hill and Steina and Woody Vasulka used the Rutt/Etra Scan Processor to expand the scope of their experiments with electronic imaging. Between 1972 and 1974, the Vasulkas explored the possibilities of the Rutt/Etra and created one of their best known video effects in which the lighter areas of the frame pull the lines of the raster vertically and give the illusion of three-dimensional shapes. When the input signal is an image captured by a camera feed, these lines seem to adopt the contours of objects. A copy of the Rutt/Etra is found in the collection of the Experimental Television Center Ltd. at the State University of New York, Binghamton (Binghamton, N.Y., U.S.).

Description of the tool

The Rutt/Etra Scan Processor consists of three boxes on a processing rack. The first box contains the monitor and an amplifier, the second box includes the components with scanning functions, and the third box constitutes the interface with raster control units and waveform generators. Two models of the device were marketed: the RE 4-A (with a 525-line monitor) and the RE 4-B (with a 1,050-line monitor).

Brief list of materials

Modules of electronic components on a processing rack.

List of components

Display control units; waveform generators (ramp generator/sine, triangle, square waveform generator); audio interface; adder; diodes module.

Operating mode

The Rutt/Etra Scan Processor is an analog computer designed to manipulate in real time the deviation signal that generates the scanning of the raster in the cathode ray tube of the monitor. In the internal mechanism of a normal television screen, the synchronization signals are controlled by magnets that guide the movement of the yoke so as to scan the 525 lines of the cathode tube. Affixed to the other components, the cathode tube of the Rutt/Etra Scan Processor has improved yokes able to measure or calibrate the voltage of the video and audio signal. The modulations affect the network of scanned lines, which are deflected so as to allow specific display functions. The functions are operated without generating distortion or affecting the resolution of the image. Unlike other analog computers in which the voltage control is dependent on patch programmable functions (for example, Daniel Sandin’s Image Processor), the functions of the Rutt/Etra Scan Processor are activated with knobs and others units on the control panels. The display control units include clockwise and counter-clockwise rotating knobs to precisely regulate the voltage directed to the cathode display. Some functions help expand or compress the dimensions of the raster by varying the amplitude of vertical (height) or horizontal (width) scanning. The parallel modification of height and width of the raster generates a depth effect similar to a camera zoom. It is possible to vary the intensity through a grey scale. Other control units give the impression that the raster is moving from left to right or from bottom to top (or the opposite way depending on the direction in which the knobs are turned). It is also possible to select a region of the image, turn it upside down and move it in various directions (this function is available only with certain copies of the Rutt/Etra Scan Processor). Waveform generators (ramp generator/square and sine wave generator) can manipulate the raster according to a regular pulse using potentiometers (or control voltage units). These components feed an electric current directly into the deviation circuitry. The ramp generator controls the current with a timing device that allows a modification of voltage in a continuous mode through a specific time frame from 0 to 10 volts (in one direction only). When linked to other control units, this generator creates automatic animation effects. Unlike the ramp generator emitting a voltage-scaled waveform, continuous waveform generators animate the forms via a continuously rising and descending signal. Knobs vary the voltage (from high to low frequency levels and vice versa), and switches fix it in three modes: low, medium and high. Another function displays the wave in a sine, triangle or square form. The audio interface routes the signal so it affects both the audio and video information when the control units and waveform generators are used. The adder mixes the input of two or more sources wired to the Rutt/Etra Scan Processor (cameras, microphones, tape decks and keyers) and juxtaposes the display of effects generated by the control units and the waveform generators. Thanks to 10 entry points to the diodes, the diodes module enables a cable to be hooked up to the input point of a control unit and/or waveform generator in order to emit an electrical current opposite the one circulating in the component so as to generate the opposite effect on the spot. To record the effects generated by raster manipulation, the screen of the Rutt/Etra Scan Processor must be rescanned with a second camera (preferably equipped with a high-definition lens) emitting a signal routed to a tape deck or other signal-processing devices. The RE 4-B with a 1,050-line monitor has a scanning rate twice the capacity of the RE 4-A and therefore captures the alteration of the raster without loss of resolution.


Controlling the scanning of the raster in the cathode ray tube, creating raster animation; generating video waveforms; generating audio content with video waveforms; generating video waveforms with audio content.

Consulted documents 

Vasulka, Woody. — [Interview with Bill Etra]. — 27 p. — Manuscript. — Interview report. 

Burris, Jon. — [Interview with Steve Rutt]. — 34 p. — Manuscript. — Transcription. 

Instant animation : Rutt electrophysics. — [s.d.]. — [1] p. — Advertisement document. — Included in the file entitled "Etra, Bill" and "Rutt/Etra scan processor". 

RE video synthesizer systems : models RE4-A and RE4-B . — New York : Rutt Electrophysics, [1974]. — 21 p. — Instruction manual. — Included in the file entitled "Rutt/Etra scan processor". 

Vasulka, Woody ; Vasulka, Steina. — Eigenwelt der Apparatewelt : Pioniere der Elektronischen Kunst = Pioneers of electronic art. — Artistic direction by Peter Weibel, edited by David Dunn. — Santa Fe : The Vasulkas ; Linz : Ars Electronica Center, 1992. — 240 p. Also available on the Internet : [ref. September 23, 2003].