The monoscope For decades a fixed image was 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 60s and 70sbut up to most of the 90s often happened to turn on the TV and find themselves in front of a Relicy of geometric figures, 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 1930sthe 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 the 1939 there RCA made the so -called famous in the United States “Indian head”: a monoscope where an American native headed at the top of the image.
In Italy Rai adopted his own Black and white monoscopepersonalized with numbers and indications of the transmission center. To generate the image you could initially use one Aluminum slab with graphiteframed by a camera, or hand designed signs. Over time these craft solutions were replaced by electronic video generatorsoften accompanied by a fixed tone at 400 or 1000 Hz, also useful for verifying 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 it 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 – they served to test chromatic loyalty. In the lower part are found 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 “Spillo”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 1992limiting himself to re -proposing it monthly for technical tests, then ceased in 2012.
