Philips circle pattern

The Philips circle pattern (also referred to as the Philips pattern or PTV Circle pattern) refers to a family of related electronically generated complex television station colour test cards. The content and layout of the original colour circle pattern was designed by Danish engineer Finn Hendil (1939–2011) in the Philips TV & Test Equipment laboratory in Amager (moved to Brøndby Municipality in 1989) near Copenhagen under supervision of chief engineer Erik Helmer Nielsen in 1966–67, largely building on their previous work with the monochrome PM5540 pattern. The first piece of equipment, the PM5544 colour pattern generator, which generates the pattern, was made by Finn Hendil and his group in 1968–69. The same team would also develop the Spanish TVE colour test card in 1973. Since the widespread introduction of the original PM5544 from the early-1970s, the Philips Pattern has become one of the most commonly used test cards, with only the SMPTE and EBU colour bars as well as the BBC's Test Card F coming close to its usage. The Philips circle pattern was later incorporated into other test pattern generators from Philips itself, as well as test pattern generators from various other manufacturers. Equipment from Philips and succeeding companies which generate the circle pattern are the PM5544, PM5534, PM5535, PM5644, PT5210, PT5230 and PT5300. Other related (non circle pattern) test card generators by Philips are the PM5400 (TV serviceman) family, PM5515/16/18, PM5519, PM5520 (monochrome), PM5522 (PAL), PM5540 (monochrome), PM5547, PM5552 and PM5631.

Operation

Rather than previous test card approaches that worked by a live camera or monoscope filming a printed card, the Philips PM5544 generates the test patterns fully using electronic circuits, with separate paths for Y, R-Y and B-Y colour components ( Y ′ U V {\displaystyle Y'UV} ), allowing engineers to reliably test and adjust transmitters and receivers for signal disturbances and colour separation, for instance for PAL broadcasts. In simple terms, the displayed pattern provides reference levels of black, white and colour saturation, to which a receiver can be set. Displayed image geometry (image centering, correct proportions of the circle, etc.) can also be corrected. More technical adjustments are also possible. Main technical features of the test card:

Circle with b/w and colour information Square wave – repeating black and white (75% amplitude) blocks resembling a (same amplitude as the colour bar); Colour bar – yellow, cyan, green, magenta, red and blue with 100% saturation and 75% amplitude (EBU colour bars); Crossed lines – at the centre of the circle, they allow to check for proper interlace; Definition lines – sine wave gratings with TV line frequencies corresponding to: 0.8, 1.8, 2.8, 3.8 and 4.8 MHz (PAL-B/G); 1.5, 2.5, 3.5, 4.0, 4.5 and 5.25 MHz (PAL-I); 0.8, 1.8, 2.8, 3.8, 4.8 and 5.63 MHz (PAL-D/K); 0.5, 1.0, 2.0, 3.0 and 4.0 MHz (NTSC/PAL-M/PAL-N); 0.8, 1.8, 2.8, 1.8 and 0.8 MHz (SECAM-L); Stair case – greyscale with 6 levels (can display up to 11); White black step with needle pulse; Colour step – red on yellow background colours, 75% amplitude. To the left of the circle: Vertical bar – line alternating positive and negative R-Y signal; Vertical bars – positive and negative R-Y signal; Two rectangles – G-Y signal. To the right of the circle: Vertical bar – line alternating positive and negative B-Y signal; Vertical bars – positive and negative B-Y signal; Two rectangles – G-Y signal. Background: Grid – made from 14 horizontal x 19 vertical lines; Background Level – adjustable between 0 and 80% amplitude; B/W border castellations.

Pattern variations

4:3 (original) While the basic specifications of the pattern normally remain consistent, there are often small variations depending on the brand and type of generator used to produce it, as well as how the broadcaster has chosen to configure it. Some television stations have included a digital clock and/or date, as well as the station logo or ID, inside the circle. This practice was common in Asia and some parts of Europe, as well as in South Africa.

SECAM The Philips circle pattern is geared towards the PAL colour-coding system, but SECAM versions do exist (for example, it was used by TVP in Poland, MTV in Hungary and TDF in France, without side bars, as well as ERT in Greece, VTV in Vietnam and Télé Sahel in Niger, with side bars). The most obvious difference is the absence of PAL specific test features (to two normally invisible outmost vertical bars). Less noticeable is the change to the multiburst gratings, instead at 0.8, 1.8, 2.8, 1.8 and 0.8 MHz due to the lower luminance bandwidth in the SECAM system.

NTSC Likewise, there are 525-lines NTSC versions of the pattern. One of the NTSC variants, used in Philippines, Taiwan, Haiti and Japan (by NHK, with the multiburst gratings slightly modified for NTSC-J), has a modified square wave near the top of the circle at 300 kHz and the multiburst gratings at 0.5, 1.0, 2.0, 3.0 and 4.0 MHz. (WNYW's configuration simply removed the side colour bars.) A second variation, used by CBC Montreal in Quebec, Canada, had different gratings and added extra colour bars.

PAL-M In addition to the 525-line NTSC pattern, a PAL-M version of the pattern was also offered for the Brazilian market. Although no public transmissions are known to exist as of August 2026, the pattern is identical to NTSC but also includes achromatic fields adjacent to the side bars.

PAL-N Though as of August 2026 no surviving equipment or captures/recordings are known, a version of the pattern existed for the PAL-N system. It is expected to resemble the PAL-B/G pattern however with the gratings of the NTSC version.

BBC Test Card G Test card G was a quasi-Philips pattern developed by the BBC. It is realised by the physical modification of standard PM5544 generators and differs from the original as follows:

Colour bar saturation - 95% (changed from 75%) Colour bar contrast - 75% (changed from 100%) Colour bar set-up - 25% (changed from 0%) Multiburst gratings (see PAL-I listing above) Multiburst amplitude - 71.4% (changed from 100%) The above specifications were incorporated back into standard Philips generators such as the PM5534I/00 and the PM5644I/00.

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