Hi to all,
the famous ABC logo is ( the lissajous pattern ) is to be replaced with a new and very boring one that just says "ABC1" - a slavish imitation of the British BBC.
The old logo will supposedly be still seen, but is no longer the primary one.
As some of you would know, the old ABC logo can be produced on the screen of any analogue CRO using X-Y ( ie horizontal & vertical ) mode using two audio generators - one generator for each axis. The famous pattern is obtained when the frequencies are set to an exact ratio of 3:1, the higher frequency being used for the vertical.
A small error in the frequency ratio causes the pattern to rotate, just as it once did when ABC used it on air as their station ID.
Lissajous patterns can be produced with any ratio of two frequencies; a 1:1 ratio results in a circular pattern and if the ratio is exact, the pattern becomes stationary appearing to be an ellipse or a circle depending on the relative phase of the two generators.
It is possible to go further with these patterns if one generator can output a square wave - likewise the use of a simple 90 degree phase shift network allows only one generator to produce a circular pattern on the screen. A second generator is then able to " modulate " that circle into some surprising patterns. These patterns will be seen as spinning on the CRO screen unless the frequency ratios are exact and locked in phase.
I have posted four attractive looking examples of what can be produced on ABSE - "alt.binaries.schematics.electronic"
Any Google Groups uses will have to get themselves a REAL newsreader to see them.