The monoscope was for decades a fixed image broadcast by Italian television (and not only) in the moments when the programs were not on air. If today we are used to a continuous and uninterrupted flow of transmissions, things were once differently. Many inevitably associate it with the 60s and 70s, but up to most of the 90s it often happened to turn on the TV and find a lattice of geometric figures in front of it, circles and bars accompanied by a continuous sound. That image was not a simple “filler”: it was used for technicians to control the quality of the transmission and viewers to regulate their device, calibrating brightness, contrast and, with the arrival of color, also chromatic saturation. To be more precise, the term “monoscope” indicates both the image itself and the electronic device that generated it.
The first monoscopes were very simple. In the 1930s, the English broadcaster BBC He experienced decidedly rudimentary versions, which consisted of a light background on which a circumference and a straight line appeared, both black. In 1939 the RCA The so -called “Indian head” made famous in the United States: a monoscope where an American native headed at the top of the image.
In Italy Rai adopted its own black and white monoscope, personalized with numbers and indications of the transmission center. To generate the image you could initially use an aluminum slab with graphite, framed by a camera, or hand designed signs. Over time, these artisan solutions were replaced by electronic video generators, often accompanied by a fixed tone to 400 or 1000 Hz, also useful for verifying the audio. In the last minutes before the start of the programs, Rai preferred instead to spread music songs, in a ritual that became familiar to millions of spectators.
In a monoscope no detail is left to chance: each section of the image corresponds to a technical test. The central circle was used to verify the geometry of the image and the correct functioning of the deflection circuits, while the white lattice allowed the control of the linearity and convergence of the pixels. The color bars – introduced with the PAL system in the 1960s – served to test chromatic loyalty. In the lower part there are gray stairs to regulate brightness and contrast, while the growing frequency sequences (multiburst) showed the TV response to the different bands: 0.8 MHz; 1.8 MHz; 2.8 MHz; 3,8 MHz and 4.8 MHz. Some bars, such as the lateral ones, served to isolate the components of the chromatic signal, while the so -called “pin”, a thin line in the white field, reveals any reflections or disorders in reception.
With the advent of color broadcasts, private TV and finally of continuous programming, the monoscope has lost its daily function. In the 80s and 90s, many local networks replaced him with the so -called “night rollers”, that is, the schedule repeated in loop. Rai abandoned him in 1992, limiting himself to re -proposing it monthly for technical tests, then ceased in 2012.
